This helped businesses like Cars.com, Autotrader.com and Edmunds.com  prosper and grow.

But what Google giveth, Google eventually taketh away, as just about every business sector has learned by now. And it appears that online car sites are about to be the latest to learn this sometimes bitter lesson.

Since last summer, Google has been experimenting with running its own car-listing service in the San Francisco area, allowing consumers to browse dealers' inventory and check prices without leaving Google's pages.

That pilot is now about to be extended throughout California and, presumably, into other states. Google did something similar with travel information last year. You can now check flights from SFO to IAD, for example, and get an instant answer right on Google's search page.

This has perhaps not been a good thing for Expedia, Kayak, et. al. but we haven't heard any consumers complaining. For one thing, the results are rendered instanteously, without the lengthy waits would-be travelers used to encounter. For another, they appear to be objective -- not favoring one carrier or agent over another, something that isn't necessarily true with many travel sites.

Come on down ...

Of course, it's not like Google will be selling cars directly. You'll still have to go to a dealer or the individual who's trying to sell what you're hoping to buy, at least for now.

And it's not like this is something completely new. Dealers say that more than 90 percent of car buyers begin their shopping online and something like two out of every three visitors who wander onto a dealership's website get there through a Google search.

According to Automotive News, dealers who sign up with Google will be able to  list their new-vehicle inventories with no upfront or monthly fees. They will, however, pay Google for the leads they get. As with all things Google, dealers will have to bid for placement in the results. It's thought the average per-lead fee will be around $15