The S&P 500 (^GSPC) includes 500 of the largest stocks in the U.S. market, but there's a huge disparity between the smallest stocks in the index and the largest ones. Recently, online-search giant Google (GOOG) has seen its share-price soar, and the stock's market capitalization briefly overtook that of oil behemoth ExxonMobil (NYSE:XOM) during Friday's trading before falling back somewhat. Yet even though investors would likely applaud the roughly 17% profit they could earn if Google continued growing enough to overtake top-ranked Apple (NASDAQ:AAPL), the fact is that reigns atop the S&P throne have historically given way to some dramatic falls. Could Google be next?

The long list of has-been big stocks
The problem that companies have with getting big is that investors expect them to stay big. But as it turns out, that's surprisingly difficult to do. In the history of the stock market, six companies have managed to hit the half-trillion-dollar mark in market capitalization, with three of them being tech stocks.

Even though Apple remains in the top spot, its market cap is well off its highs. In late 2012, the company was worth about $650 billion, but even after an impressive bounce from last year's lows, its market cap is roughly 30% below that level.

That might sound like a substantial drop, but it's nothing compared to other past tech high-flyers. In 2000, Intel (NASDAQ:INTC) briefly topped $500 billion in market cap, as its almost-unchallenged dominance of the PC industry pointed to a rich future. Now, it stands more than three-quarters below that level, as the rise of the mobile revolution has threatened to slaughter its cash cow and leave it trying to sell obsolete technology. Microsoft (MSFT) has lost about half its market cap since its peak value of $613 billion in late 1999.

Cisco Systems (NASDAQ:CSCO) has had an even bigger fall from grace. Having been the biggest company in the market briefly in sporting a $550 billion market cap 14 years ago, the networking giant promised to take full advantage of the Internet's rise. Yet the tech bust left the stock particularly hard hit, and now, a nearly 80% drop in market cap reflects concerns that smaller competitors have already dislodged Cisco from the leadership role in the networking industry.

Yet technology stocks aren't the only ones to suffer from leadership anxiety. General Electric (NYSE:GE) took over the top-stock role in late 2000, almost hitting $600 billion in market cap. One financial crisis later, GE sports a market cap almost 60% lower, despite having rebounded sharply in the aftermath of the market meltdown of 2008 and early 2009. Even Exxon is down by about a quarter from its highs, as the oil giant hasn't been able to replicate the success that sent its stock soaring when oil approached $150 per barrel briefly in late 2007.

The No. 1 curse?
Obviously, it's premature to talk about Google being the No. 1 stock in the market, since it still has substantial ground to gain on Apple before dethroning the iPhone maker. So far, the online-search company seems to be firing on all cylinders, with recent decisions divesting itself of its Motorola Mobility division, agreeing to a cross-licensing deal with Samsung, and buying some smaller companies to expand its reach in artificial intelligence.

In the end, the only limit to a company's value is its ability to grow profits. Although natural impediments like antitrust law tend to stop many companies from growing beyond a certain point, Google won't automatically be doomed to the same fate as its predecessors even if it does eventually leapfrog Apple to take over the top spot in the market.

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.