The Rubicon Project, a meta ad network that helps Websites place and optimize ads from the hundreds of other ad networks out there, closed a $15 million B round just three months after raising a $6 million A round. Hopefully, they didn’t spend it all already. The B round was led by Mayfield. IDG Ventures Asia, Stanford University, the University of California Berkeley, and Clearstone Venture Partners (which led the A round) participated, as did LowerMyBills founder Matt Coffin.

The company is still in beta and is not charging customers yet, but in the past three months it has served up 4 billion ads and generated more than $1 million in revenues for its beta publishers. It claims beta customers are seeing a 30 percent+ increase in ad revenues, and is trying to figure out how much of that it can take as its fee. Ultimately, the Rubicon Project is a middleman in between a Website and another middleman (the ad network) and, finally, the advertiser. The fact that they think there is a business here speaks to the inefficiencies of the online advertising market. Maybe it is time for online advertising exchanges like Microsoft’s AdECN, which is a stock exchange for ads where buyers and sellers deal with each other directly.