Generally speaking, it pays to be bullish on Wall Street. Despite navigating its way through Black Monday in 1987, the dot-com bubble, the Great Recession, and more recently the coronavirus crash, the average annual total return for the benchmark S&P 500 since 1980, including dividends, is north of 11%.

Not surprisingly, we see this optimism readily apparent in Wall Street's ratings on stocks. According to FactSet, more than half of all stocks carry a consensus buy rating, 38% have the equivalent of a hold rating, and just 7% are rated as sells. Yet, history shows that far more than 7% of stocks will eventually head lower. 

Based on Wall Street's consensus price targets, the following five ultra-popular stocks are all expected to lose value over the coming 12 months.

A frustrated stock trader grasping his head while looking at losses on his computer monitor.

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Palantir Technologies: Implied downside of 12%

Since its direct listing in late September 2020, data-mining company Palantir Technologies (NYSE:PLTR) has been a favorite among growth and retail investors. But if Wall Street's one-year consensus price target proves accurate, Palantir will head in reverse by up to 12%.

The likeliest reason Wall Street is tempering expectations on Palantir is valuation. Specifically, Palantir ended June 17 with a market cap of nearly $48 billion, but is on track to bring in perhaps $1.5 billion in full-year sales in 2021. That's a multiple of about 32 times sales. Even if Palantir continues to grow its top-line at 30% annually, it could take years for this price-to-sales multiple to come down to anywhere close to the average for cloud stocks.

Another possible concern is the growth potential for its government-focused Gotham platform. Big government contract wins in the U.S. have been primarily responsible for Palantir's exceptional growth rate. However, there remains an outside chance that President Joe Biden may curb funding to some of the federal agencies that employ Palantir's services.

Over the long run, I'm optimistic and believe Palantir's platform is unlike anything else available. But tempering near-term expectations given its valuation premium may be warranted.

A physician administering a vaccine into the right arm of a young woman.

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Moderna: Implied downside of 11%

Biotech stock Moderna (NASDAQ:MRNA) is arguably the biggest beneficiary of the coronavirus disease 2019 (COVID-19) pandemic. It's one of only three drugmakers to currently have their COVID-19 vaccine approved on an emergency-use authorization (EUA) basis in the United States. But if Wall Street's consensus 12-month price target is correct, it's stock is also on its way to a double-digit decline.

Why the lack of love from Wall Street? The answer looks to be analysts looking to the future. While Moderna's COVID-19 vaccine is a mainstay in the U.S., and it's likely to play a clear role in other markets, time might prove the company's enemy. Over time, new vaccines are expected to come onto the scene, which'll eat away at Moderna's potential pool of patients.

The other worry is that no one is exactly certain how long COVID-19 vaccine immunity will last. If it's a year, Moderna is unlikely to be the only drugmaker supplying booster shots. Meanwhile, if it's longer than a year, it means reduced sales opportunities for the company.

Based solely on Wall Street's earnings per share consensus in 2021 and 2022, Moderna appears reasonably priced. But with the company staring down a potentially significant haircut in revenue next year as new drugmakers enter the space, caution is advised.

A father and son playing video games while seated on a couch.

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GameStop: Implied downside of 71%

This will probably come as a shock to no one, but Reddit favorite GameStop (NYSE:GME) is fully expected to fall flat on its face. Even though Wall Street's consensus price target for the company has quintupled in recent months, it still implies up to 71% downside over the next year.

The biggest issue for GameStop is that its valuation has completely detached from its underlying fundamentals. While it's not uncommon for stocks to trade on emotion for short periods of time, operating performance is what always dictates the long-term movement in the share price of a stock. When it comes to operating performance, GameStop has been a dud.

Although the company's first-quarter fiscal results highlighted a 25% net sales increase from the prior-year period, total sales for the company have been falling precipitously for years. That's because video game retailer GameStop recognized the shift to digital gaming too late, and it's now stuck with its massive portfolio of brick-and-mortar gaming stores. Even though e-commerce sales have been a bright spot for the company, slashing costs and closing stores remains its No. 1 priority. 

With sufficient cash, bankruptcy isn't a concern for GameStop. But without any true top-line growth and the company still losing money, it's an impossible sell at its current price tag.

A handful of syringes lying atop a messy pile of one hundred dollar bills.

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Ocugen: Implied downside of 18%

Volatile clinical-stage biotech stock Ocugen (NASDAQ:OCGN) may also be in for an unpleasant next 12 months. The company behind an experimental COVID-19 vaccine (Covaxin) and a trio of internally developed eye-blindness candidates is expected to shed 18% of its value, if Wall Street's consensus price target is correct.

Arguably the biggest issue for Ocugen is the clinical update the company issued on June 10 concerning Covaxin. Even though partner Bharat Biotech led a large clinical study in India that yielded an overall efficacy of 78%, along with 100% efficacy in preventing severe forms of COVID-19, Ocugen announced on June 10 that it would forgo seeking an EUA in the U.S. and would instead file for a biologics license application. In other words, Ocugen's path to a quick emergency approval in the U.S. just flew out the window. 

What's more, the U.S. Food and Drug Administration's requested additional information and data on Covaxin. This is a fancy of saying that Ocugen will very likely have to run a clinical study in the U.S. prior to submitting Covaxin for approval. That means added costs and an even longer wait before Ocugen has a chance to penetrate the lucrative U.S. market.

Though it's impossible to predict how long COVID-19 vaccine immunity will last, Ocugen's chances of being a significant player in the U.S. COVID-19 vaccine space are dwindling.

A row of graphics processing units used for cryptocurrency mining.

Image source: Getty Images.

NVIDIA: Implied downside of 3%

Don't adjust your computer, laptop, or smartphone screens -- that really says NVIDIA (NASDAQ:NVDA). Following its incredible run higher (NVIDIA has doubled over the past year), graphics processing unit giant NVIDIA closed 3% above Wall Street's consensus price target, as of June 17.

One reason for tempered expectations at this point has to be valuation. Even with NVIDIA crushing expectations and seeing strong PC gaming demand, sales growth is expected to slow from an estimated 49% in fiscal 2022 to a high single digit percentage in each of the next two fiscal years. In fact, the company closed at nearly 20 times projected sales for the current fiscal year. That's a bit optimistic given an expected sales growth slowdown.

Perhaps the other reason Wall Street expects NVIDIA to go sideways is the company's cryptocurrency mining chip segment. While sales of crypto chips could hit $400 million in the current quarter, demand is entirely dependent on the hype surrounding digital currencies and the favorability of technical charts. Crypto is just as well known for its long bear markets as it is for the big gains it's delivered over the past decade. If another lull strikes, a fast-growing ancillary segment for NVIDA could easily become a drag. 

For what it's worth, I see no fundamental reasons to sell NVIDIA if you're already a long-term shareholder. But if you're on the outside looking in, I don't exactly see $746 as an attractive entry point, either.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.