Bat got your tongue? We dare you to keep reading our special series on the World’s Scariest Stocks.

Investors are a lot like a girl in a horror movie. The reason that the girl is screaming -- in my analogy, the reason investors are selling -- isn't because of what's outside her house. She's screaming because she doesn't know what's outside the house.

The fear of the unknown makes investing scary, and things don't get much more unknown than the future of Dendreon (NASDAQ:DNDN). The biotech is up for its second nomination as the World's Scariest Stock in as many years, and being a year older hasn't made it any less so.

A brief history (the scary known)
Unfortunately, knowing Dendreon's history doesn't make it any less scary. At least with stocks like Eli Lilly (NYSE:LLY), Pfizer (NYSE:PFE), or Johnson & Johnson (NYSE:JNJ), you've got a long history of increasing dividends to cushion the fear. The rollercoaster that Dendreon's stock has been on only increases the anxiety.

The stock jumped from $4 to $25 after a Food and Drug Administration advisory committee recommended approval of its prostate cancer treatment Provenge last year ... only to fall to $6 after the FDA decided that it needed to see more efficacy data. While volatility can make investors money, that's a roller coaster that could make even the bravest investor's stomach turn.

The trial to satisfy the FDA's curiosity is underway. An interim peek at the data earlier this month didn't do anything but raise the threshold that Provenge must reach to pass muster when the final data comes in.

The future (the scary unknown)
Now investors just need to wait. And wait. And wait some more until the trial concludes some time next year.

What's the chance of success of Dendreon's pivotal trial? It seems like a crapshoot to me. The data is trending toward the treatment extending the lives of cancer patients, but whether the trial is large enough to show a statistically significant effect is the $1 billion question.

Here's the big problem: Dendreon is Provenge, and as Provenge goes, so goes the company, to maul a phrase. Dendreon actually has one phase 1 drug and a handful of preclinical candidates, but they're not likely to offer much value to investors if Provenge fails.

Compare that to other developmental-stage drugmakers with multiple shots on goal, like Exelixis (NASDAQ:EXEL) or Seattle Genetics (NASDAQ:SGEN). If one of their drugs fails, there's another to take its place in the clinic. Dendreon, on the other hand, is destined either to become the next Cell Genesys or Onyx Pharmaceuticals (NASDAQ:ONXX) -- penny stock or one-hit wonder -- all depending on Provenge.

Gets your guts
I'm fully aware that biotechs can offer investors some serious rewards, but at this point, I just don't see the benefit of owning Dendreon shares. It's trading at a market cap of about $450 million right now, and I'd estimate it might be worth about $1.2 billion if Provenge has a positive phase 3 trial. While tripling your money sounds pretty good, it comes with a fair amount of risk that's hard to quantify. It seems better to hit the lobs rather than trying to swing for a homerun and strike out because your eyes are closed.

At some point, Dendreon might get to a price that I can't resist, but at this point it remains a very scary stock for the immediate future.

If you agree, join me in voting Dendreon as an underperform in Motley Fool Caps. If, however, you're not afraid of ghosts or goblins, then mark it to outperform the S&P 500. And be sure to check back here to see if Dendreon indeed wins the right to be called the World's Scariest Stock.

Pfizer, Eli Lilly, and Johnson & Johnson are Motley Fool Income Investor selections. Pfizer is also an Inside Value pick, while Exelixis is a Rule Breakers recommendation. The Fool owns shares of Pfizer and Exelixis. Try any of our Foolish newsletters today, free for 30 days.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool's disclosure policy isn't scary at all.