Accel Partners

Business-networking site LinkedIn, facing more competition as other sites court business users, replaced its chief executive Wednesday with one of the company's cofounders. Reid Hoffman took over as CEO, a position that had been held by Dan Nye.

Jeff Weiner, a former Yahoo executive vice president, will become "interim president," handling day-to-day activities and overseeing all company executives.

In what marks a positive sign in a struggling economy, AdMob on Wednesday announced it has achieved positive cash flow and secured a $15.7 million Series C investment fund.

Led by Sequoia Capital's Growth Fund -- with existing investor Accel Partners also participating -- AdMob intends to use the cash infusion to expand its market position in mobile advertising. The company has posted strong year-over-year growth. In fact, the mobile-advertising platform more than tripled the number of ads served on a monthly basis to 4.5 billion in September.

Marc Andreessen, an entrepreneur and software engineer behind the Web's earliest browsers, has joined the board of the online hangout Facebook.

Andreessen's appointment could bring additional clout and insight to a young but growing startup headed by Mark Zuckerberg, 24, who started Facebook as a Harvard undergraduate.

Flickr founders Stewart Butterfield and Caterina Fake have joined the parade of executives leaving Yahoo. Flake officially left the company Friday, while Butterfield will leave on July 12. He will be replaced by product-management director Kakul Srivastava.