Google and Yahoo get sued on a regular basis, often by tiny outfits with no chance of winning.  But now, the two companies are facing a much more serious lawsuit, as Xerox, which has a market cap of almost $8 billion and a genuine legal team, is taking them to court.

Xerox claims that Google and Yahoo have infringed on two patents it holds.  Susan Decker explained earlier this morning, "One patent, issued in 2004, is for a way to automatically generate a query based on keyword searches. . . .  The second patent, issued in 2001, is for a way of updating pages based on user reviews."

Xerox would like to be compensated for Google and Yahoo’s alleged infringement, and also wants to bar them from using the tech again without its consent (which could probably be obtained via a licensing agreement).

Of course, Google and Yahoo aren’t liable to hand Xerox a blank check.  One of Google’s lawyers has already described Xerox’s claims as being "without merit," and Carol Bartz isn’t the type to shy from a fight.

This could turn into quite a legal battle, then, and the operation of AdSense, AdWords, Google Maps, Google Video, YouTube, the Yahoo Publisher Network, Yahoo Search Marketing, Yahoo Shopping, and the Y!Q Contextual Search tool might be affected by the outcome.