Yahoo has thousands of patents while Facebook has 62, according to the United States Patent and Trademark Office (USPTO). Those are the ones that have been filed in each of the companies' names; both firms have more patents each, but either way Yahoo has significantly more than Facebook.
Typically in situations like this one, the company being sued looks through its own patent portfolio, files a counter lawsuit, and negotiates to pay (or receive) some money, and the two agree to settle. The problem is Facebook has very few patents. As such, it will be very hard for Facebook to settle with Yahoo, but apparently that's the route Facebook is planning to take, according to this new rumor. We'll see soon enough how Facebook will play its hand, but the final decision will likely be drawn out, as with any patent battle.