It's one thing to represent someone who has a questionable case. It's quite another to continue to press forward with a lawsuit when you have evidence that the case is not only questionable, but fraudulent.
If Facebook is to be believed, that's exactly what the multi-firm team that represented Paul Ceglia did. Ceglia claimed that Facebook founder Mark Zuckerberg sold him an ownership stake (now worth billions) in his startup social network. Ceglia's lawsuit was dismissed after evidence emerged that the contract he presented as proof of a deal was a forgery.
Fresh off that victory, Facebook isn't pursuing Ceglia for the false claims; the company is suing his lawyers.