Andreessen Horowitz has invested more than $80 million in Twitter via purchasing stock in private secondary markets.

When called about it by BoomTown, a spokeswoman at the high-profile Silicon Valley venture firm confirmed the purchase.

To be clear, Twitter does not get this money--early investors and employees able to sell their privately held Twitter shares do.

Buying into the secondary markets--which have recently attracted some controversy and regulatory scrutiny--has become a common way for VCs to invest in a hot start-up without a complex and competitive funding bake-off.

The move is an interesting one, since Andreessen Horowitz was not part of the recent $200 million round of venture funding at the San Francisco microblogging company, led by Kleiner Perkins at a $3.75 billion valuation.

Sources said that the firm made the move because it is already deeply invested in other key companies in the social space, including gaming giant Zynga, location-focused Foursquare, local discounting phenom Groupon, and general social-networking behemoth Facebook.

Apparently, Twitter makes it a full basketball team.

The investment by the firm gives more perceptual boost to Twitter, which is still trying to create a lucrative business model for itself, focused on advertising.

It needs to, if it want to stay independent for the long haul.

While an IPO is a possibility, so is an acquisition. Several months ago, while it was doing its funding round, Twitter had incoming interest from Facebook, which lobbed in a $5 billion soft offer, as well from Google.

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