Biogen Idec and partner Elan had to pull their multiple sclerosis drug Tysabri after patients in clinical trials came down with a rare viral disorder that can lead to brain damage or death.

FORBES: Genentech's Next Act

Verizon is a stronger partner, and its management team has proved itself able to successfully pull off big mergers.

FORBES: Call It Quits, Qwest

In a research note, Scott Sweet, IPO Boutique senior managing partner, said there hasn't been an IPO that has exuded such a pull on investors since Google Inc.

WSJ: IPO Analysts Warn of Longer-Term Facebook Risks