Nov 20, 2010 12:05 GMT  ·  By

Facebook seems unstoppable now and it's valuation is going through the roof. The latest estimates put it at $35 billion to $40 billion, though it's hard to know for sure until the company goes public. Facebook largest VC investor has sold a hefty chunk of its share, making perhaps $500 million in the process.

TechCrunch reports that Accel Partners, which had been the largest venture capital investor in Facebook, sold about one fifth of its shares, or effectively two percent of Facebook.

Accel Partners owned 10 percent of the social network being one of the first investors. The VC firm put in $12.7 million for 10 percent of the company five years ago. Needless to say, Facebook value went through the roof since.

The rumor says that the firm sold the shares at a $35 billion valuation for Facebook. TechCrunch estimates that Accel Partners sold less than 20 percent of its stake for $500 million, a 247 times return on the initial investment.

Of course, the venture capital firm still owns more than eight percent of Facebook, worth at least $3 billion. At this point, the firm may not be the largest investor in Facebook.

Mail.ru Group, formerly known as DST, the Russian investment company has been buying up Facebook shares, with direct investments as well as buying shares from Facebook former employees and other small investors. Mail.ru's stake in Facebook was estimated at five percent last year and it may be bigger now.

Facebook's current worth is based on transactions on the secondary markets. The latest estimates go as high as $40 billion. Of course, there's no way to know for sure how much Facebook is worth until it goes public and that may be at least a couple of years away.