Limited partners have been complaining for years they are putting more money into life science ventures than they are getting out. But if the M&A returns for 2011 are maintained, the trend could be reversing.

The amount of cash returned to VCs from private M&A deals in 2011 surpassed the total amount of capital invested into private biotechs - a feat that hadn't occurred in the prior five years, according to an analysis by Atlas Venture's Bruce Booth.