Facebook has acquired 750 patents from IBM, in a deal that has not yet been announced publicly by the companies, Bloomberg Businessweek reported today.

The move will help rectify a problem exposed by Yahoo's patent lawsuit against Facebook—namely, that the company doesn't have enough patents to deter lawsuits from rivals. While acquiring patents has no direct impact on the validity of Yahoo's claim, a bigger and stronger portfolio would increase Facebook's options now and in the long run, as we noted in a story last week. For example, a well-placed countersuit could lead to a mutually beneficial licensing agreement. Additionally, adding to Facebook's patent stash opens up the possibility of launching suits against other rivals.

A search of the US patent database shows Facebook owning just 21 US patents—although Businessweek said the company actually has 56 patents and 503 pending applications. Still, Facebook's patent portfolio is dwarfed by Yahoo's, which has more than 1,000. IBM has plenty to spare, having been granted 6,180 US patents in 2011 alone, the 19th consecutive year IBM topped the list of patent recipients.

Yahoo claimed Facebook infringes ten patents covering social networking, privacy, messaging, advertising, and website customization. We don't know exactly which patents Facebook is getting from IBM. Businessweek said only that the patents "cover various technologies such as software and networking," a description that likely applies to many thousands of IBM patents. IBM also sold 200 patents to Google in January, and another 1,000 to Google last year.