The ad network Federated Media has raised $50 million at a $200 million pre-money valuation from private equity firm Oak Hill Capital Partners, I’ve heard from a source, with investment bank Savvian helping to broker the deal.

A couple of weeks ago, a separate source told me that FM was close to raising $30 million at the same valuation. At that time, Valleywag reported that fundraising wasn’t as far along as my source claimed.

Federated Media isn’t commenting on this latest rumor, and it tells me that it will let me know if or when it has news to share.

The Sausalito, Calif.-based company generated roughly $20 million to $23 million in revenue last year (not profit), according to one of the sources. Both sources say that FM is on target to make around $60 million this year, with some profit.

Many people looked at the deal and passed, said one source, but apparently it has had a solid bite.

FM sells ads for more than 200 web publishers [Disclosure: Including VentureBeat]. Some, like one commenter on our last story on FM funding, are questioning whether or not FM is actually worth this much money, as there are many advertising options available to publishers.

But Federated Media keeps on growing, and it has also been trying out some interesting forms of advertising on social networks. It has run a successful campaign with Dell on Facebook application Graffiti, an effort by Dell to brand itself as being environmentally friendly. Graffiti is an application where users can share their digital art with each other, so in this campaign, Dell held a contest for users to submit “green”-themed art.

More recently, FM and Graffiti have done the same sort of contest, but with car-maker BMW. The theme isn’t “green” — users answer the question “what drives you?” with art.