Round three of Carl Icahn vs. Biogen Idec (NASDAQ:BIIB) has just begun. Two years ago, the billionaire activist investor waged a proxy fight to get seats on the company's board, to no avail. In round two, investors gave him two of the three seats he asked for. During intermission, CEO James Mullen retired, amid speculation that he wasn't interested in going another round.

Icahn still has fight in him, though. Yesterday, Biogen said it had received word that Icahn plans to nominate three more people to the board. He's also asking that the bylaws be amended to fix the number of seats at 12, presumably so that Biogen can't expand its board faster than Icahn can get seats on it.

There are four spots open, but Icahn is only nominating three candidates. That might be because one of the spots belongs to Brian Posner, whom Icahn nominated to the board of Yahoo! (NASDAQ:YHOO) in 2008. If investors vote for Icahn's three nominees, and Posner wins and sides with Icahn on the Biogen board, Icahn would end up with control of half of the board.

Since the beginning, Icahn's goal has been to get Biogen sold. That probably hasn't changed much: Two of his nominees were on the board with him at ImClone Systems, where they were able to get Eli Lilly (NYSE:LLY) to outbid Bristol-Myers Squibb (NYSE:BMY) for that company.

As part of the proxy fight last year, Icahn proposed breaking Biogen in two to make it easier to sell. One half would get the Tysabri partnership with Elan (NYSE:ELN), and the other its Rituxan partnership with Roche. The two halves might be easier to sell, but I'm still not convinced that move would unleash much pent-up value.

Investors should have mixed emotions about Icahn meddling farther into Biogen's business. The company hasn't performed all that well over the last few years, and proxy fights are a major cost and distraction for the company. The only entities that might be excited about the move are Genzyme (NASDAQ:GENZ) and Amylin Pharmaceuticals (NASDAQ:AMLN), which may be hoping that Icahn is distracted enough to not come (further) after them.

Chuck Saletta wants to know whether this guy is the next Buffett. Hint: He doesn't mean Icahn.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.