Shift for SAC's Cohen

Over the years, SAC has been one of Wall Street's most successful hedge funds, making Cohen a very wealthy man. In 2006, the fund posted a 34% return, one of the best performances for any hedge fund.

SAC made its mark on Wall Street by employing dozens of fast-money traders who didn't hold onto positions for long. But in more recent years, SAC has taken big positions in companies and agitated for change, such as buybacks, dividends or corporate buyouts.

Then again, there's some logic to big hedge funds like SAC getting involved in private equity deals. The market for LBOs is on fire, and private equity firms have been scoring big profits by taking companies private and then unloading them a year or two later in an IPO or a subsequent sale.

Buyout firms in the U.S. are flush with cash after raising more than $200 billion last year from institutional investors seeking higher yielding returns. Last year, private equity firms, on average, posted returns in excess of 25%, according to Mercer Investment Consulting.

By contrast, hedge fund returns have lagged behind of late. Last year was marked by a number of big hedge fund blowups, including the collapse of Amaranth Advisors, once a $6 billion fund. Many players in the $1 trillion hedge fund industry have found it difficult to substantially outperform the major market indexes.