Steyer's last year at Farallon was decent enough, with his flagship hedge fund returning 11.42% net, though the performance trailed the U.S. stock market.

FORBES: Thomas Steyer

Large Motorola Mobility holders like activist investor Carl Icahn and Farallon Capital Management would take a big hit if the deal were to breakdown.

FORBES: Apple Forces Google to Favor Motorola IP Over Android Profits

Steyer, 55, who is co-managing member of Farallon, will turn over responsibilities to Andrew Spokes, who has been running Farallon with Steyer for the past five years.

FORBES: California Hedge Fund Billionaire Tom Steyer To Step Down, Focus On Philanthropy

Tom Steyer announced in a letter to investors Monday that he will be stepping down from Farallon Capital Management, the hedge fund he founded in San Francisco in 1986.

FORBES: California Hedge Fund Billionaire Tom Steyer To Step Down, Focus On Philanthropy

Steyer will sell his stake in Farallon to partners.

FORBES: California Hedge Fund Billionaire Tom Steyer To Step Down, Focus On Philanthropy

The founder of Farallon Capital Management, Steyer, 55, had long been a high-giving Democratic donor and philanthropist who kept an exceedingly low profile, as my colleague Kerry Dolan wrote last year.

FORBES: Hedge Fund Billionaire Addresses Democratic Convention, Pushes Green Energy

We wondered if that was because the PowerMac G3 machine there was running a Farallon Skyline wireless PC card and Mac OS9, which the card demands, while the rest of the Macs on the network run OS X.

FORBES: Magazine Article