If you use Google products, Google probably has a fair amount of data about you. Of course, it provides a dashboard, where you can see just what they do have, and adjust accordingly, but it’s unlikely that the majority of users bother, while many probably don’t even realize it’s available to them.

Now that Google+ is out, Google is getting a whole lot more data, and if the new social network were ever to reach Facebook-like levels of usage, the amount of data would just be enormous. This kind of data has been invaluable to Facebook and its advertisers, and Google could soon have a lot more to offer its own advertisers.

On top of that, according to Michael Learmonth at AdAge, the company is building an exchange for advertisers to buy and sell data. He reports:

Here’s how a data exchange works: publishers and third-party providers, such as BlueKai and Exelate, would be able to feed their data into the market and advertisers could dip in and buy audience segments, such as people shopping for new cars or planning a trip, soccer moms in Ohio, or readers of certain sites like The New York Times. That data, attached to a cookie, is used to target advertising to the right people. Online publishers using Google’s ad server, DoubleClick, would be able to sell data on their audiences in the exchange as easily as they might sell ad space.

Google declined to comment on the specifics or offer a timetable for a data-exchange product, though executives briefed on their plans believe it is perhaps weeks away from rolling out at least some of its functionality.

After interviewing Google ad guy Neal Mohan, Learmonth also says the end result might not be a single product, but capabilities across Google’s online display infrastructure.

Google is currently in the process of trying to acquire ad optimization firm AdMeld. The purchase is currently being scrutinized by the Department of Justice. The investigation is aimed at determining if Google’s dominance in search advertising could make this an anticompetitive buy, and will examine Google’s plans for expansion strategies related to the acquisition.

“The acquisition is designed to help publishers get the most from the rapidly growing display advertising industry, which is both complicated and incredibly competitive — the emergence in recent years of a huge variety of technologies for publishers, like Admeld’s, is great evidence of that,” a Google spokesperson has been quoted as saying. The Federal Trade Commission has since launched its own antitrust investigation into Google’s broader business practices.