We tend to ignore highly volatile biotech stocks that bound off the walls and ceilings like a Happy Fun Ball on acid-laced meth, but Dendreon Corporation (DNDN) is a special case because it is such an obnoxious assassins tool for the elimination of careless shorts. (And we keep getting email tips). Short interest in Dendreon was upwards of 14 million shares on about 100 million outstanding. A very hard stock to borrow, as it happened, and susceptible to recall. But that was nothing compared to the announcement that it had fantastic results with:

…its pivotal Phase 3 IMPACT study of Provenge (suspiciously close to “revenge”) in men with advanced prostate cancer data. While the data is incomplete or non-statistical, Dendreon said that the IMPACT study met its primary endpoint of improving overall survival compared to a placebo control. Dendreon intends to file an amendment to its existing Biologic License Application (BLA) in the fourth quarter of this year to gain licensure of PROVENGE.

Being caught short was deadly for your position.

The market had been expecting an announcement within the year, and a competitor had (with the short squeeze fueling the surge). Also, a potential Provenge competitor was pulled from development late last year. Good news would be sticky.
Ouch.
Dendreon Plunge Baffles CEO as Cancer Drug Said to Prolong Life [Bloomberg]