As part of Google’s latest attempt to build a social platform alternative to Facebook, the company is reportedly buying virtual monetization service provider Jambool. The price is $55 million plus an earn-out worth between $15 million and $20 million, according to TechCrunch.

Reached by phone, Jambool cofounder Reza Hussein gave us a firm “no comment.”

Jambool, maker of the Social Gold virtual currency payments wrapper, has been busy building its business both on and off of Facebook — but mostly off, these days, as Facebook has been indicating that it plans to make its Credits virtual currency the exclusive payment option in games. Major developers including CrowdStar and Playdom have already signed on to Credits, essentially removing the need for Jambool’s multi-payment service on Facebook’s platform.

As it has been squeezed out of Facebook, Jambool’s approach has been to argue publicly against Facebook’s idea of Credits — see this recent guest post from cofounder Vikas Gupta for more on that — and to expand with other partners. One of those partners is MySpace, also a Google ally against Facebook.

Given that Google is trying to create an alternative to Facebook, and that Jambool can only really function off of Facebook, this deal seems like a good fit. Jambool’s founders, Amazon payments veterans, can help Google figure out how to integrate payments as part of a social platform. Of course, this follows Google’s recent purchase of Slide and its investment in Zynga, other moves designed to bolster its social leadership and product portfolio.

Jambool had raised $6 million in two rounds of venture funding.