The broad-based S&P 500 may have closed at its lowest level in more than two months yesterday on word that the Federal Open Market Committee was reducing its monthly bond-buying stimulus by $10 billion for a second straight month, but 41% of companies within The Motley Fool CAPS database are still within 10% or less of a 52-week high. For skeptics like me, that's an opportunity to see whether companies have earned their current valuations.

Keep in mind that some companies deserve their current valuations. Despite its premium valuation, Biogen Idec (BIIB 0.38%) still appears to have room to run higher after reporting solid fourth-quarter results yesterday. Fueling Biogen's growth were sales of $398 million of oral relapsing multiple sclerosis treatment Tecfidera, which has totaled close to $900 million in revenue in just three quarters. With a markedly better safety profile than two competing therapies, it appears that Tecfidera is a blockbuster in the making. With Biogen Idec forecasting impressive earnings-per-share growth in 2014 ($11 to $11.20 in EPS) and top-line growth of 22% to 25%, optimists have plenty of reason to believe the company can continue to soar.

Still, other companies might deserve a kick in the pants. Here's a look at three that could be worth selling.

Bingo for Vringo
The wins keep on coming for intellectual-property rights company Vringo (NASDAQ: VRNG), which confirmed yesterday that the U.S. District Court for the Eastern District of Virginia had ruled in the company's favor that Google (GOOGL -0.09%) infringed on its patents with various programs, including AdWords, which entitled Vringo to a post-judgment award of 6.5%. Vringo had already been awarded $30.5 million in a patent infringement case against Google in 2012, but apparently Google's subsequent modifications didn't end the infringement on Vringo's patents.

According to estimates from The Wall Street Journal, this award could net roughly $1 billion for Vringo, including past judgments. I'm not nearly as enthusiastic.

One factor to consider with larger patent awards like we witnessed yesterday is that Google will almost certainly appeal the ruling, which has the effect of dragging out the settlement. In addition, appeals usually cause the amount of the award to be lowered, which I would personally expect in this instance.

Even more important than the award itself is the fact that it's incredibly difficult to value a company like Vringo. Vringo's cash flow can be brutally erratic because of patent rights issues like it's dealing with now, and it can be challenging to sell its patents on the open market if the company needs to generate cash. In fact, since 2008 Vringo has delivered a cash outflow of $60 million.

With no concrete value measures and a ruling bound to get stuck in limbo for the foreseeable future, I'd use this spike in Vringo's stock to exit stage left.

Strength in numbers
While "vice stocks" encourage investors to buy into companies that make products that can be bad for our health, sometimes the best short-sale recommendations in the biotech sector are companies that target diseases that are most difficult to treat. One company that caught my attention in a not-so-positive way is Prana Biotechnology (NASDAQ: PRAN).

Before I contend with the negatives, I'd like to note that Prana has delivered a lot of excitement thus far in its ongoing research into treating Alzheimer's disease and Huntington's disease. Prana's PBT2 is in midstage studies involving the two diseases, and the company is researching PBT434 in Parkinson's disease and PBT519 as a possible therapy for brain cancer.

However, there's one primary reason I would suggest investors take at least some of their position off the table here, and that's the overwhelmingly poor history of success in treating Alzheimer's disease and other neurological disorders. This doesn't mean Prana won't succeed in its efforts to develop PBT2 into a viable drug, but history has proven otherwise.

Take, for instance, the dual failures we witnessed in 2012 from Eli Lilly's solanezumab and Pfizer and Johnson & Johnson's bapineuzumab, which both failed to meet their primary endpoints in phase 3 studies. Bapineuzumab was eventually scrapped, while solanezumab's effects are being studied over the long term in Europe. In 2013, Baxter International's late-stage Alzheimer's disease drug Gammagard also failed to meet its primary endpoint and was scrapped.

Ultimately, Prana shares have quintupled since last summer on the high hopes of success for what I consider to be a limited pipeline that consists of just two midstage studies and two early-stage studies. If PBT2 follows the path of the aforementioned Alzheimer's drugs Prana could be in for a substantial loss of value.

Headed for a wipeout?
Spinoffs have been one of the most effective methods for companies to unlock shareholder value since the recession, as better transparency has often fueled both components higher. This is one reason we've seen consumer packaged-food and beverage company WhiteWave Foods (WWAV) jump since being spun off from Dean Foods.

WhiteWave Foods rallied strongly last month after announcing the $600 million purchase of Earthbound Farm, an organic-food company, from private-equity firm Kainos Capital. WhiteWave understands that a push toward healthier eating habits, coupled with the higher prices and stronger margins that are assumed when purchasing organic foods, should add to its bottom line.

Although WhiteWave has demonstrated solid growth prior to this transaction, there are a few factors that would deter me from buying into the company here.

First, there's food inflation costs. Historically speaking, food inflation is pretty low at the moment. Also speaking historically, food costs rarely stay tame for an extended period of time, meaning WhiteWave will be forced to either absorb higher input costs or run the risk of alienating its customers by raising prices.

The other concern would be WhiteWave's premium valuation. Excluding the company's purchase of Earthbound, WhiteWave is probably capable of high-single-digit top-line growth. That isn't too bad, considering how slow growth is throughout the remainder of the sector, but at a forward P/E of nearly 27 it's a bit excessive. The only way I could see supporting this valuation is having some guarantee that consumers would be willing to absorb hefty price increases in the near future, but that seems unlikely with consumer spending still relatively weak.