Most of the patents that?Yahoo is suing Facebook?over?are for?vague concepts that underly a wide variety of web services, but one is for a much more specific protocol that Facebook definitely employs:?seamless communication between email and instant messaging users. If the other patents are ruled invalid for being too broad to enforce, it's maybe this Patent?7406501?that could stick.?Facebook could need a?separate?defense or answer to this complaint, or it could be forced into a settlement to close the case prior its IPO.