Roger Parloff at Fortune reports that Facebook is contemplating a lawsuit against the lawyers who for a time represented Paul Ceglia, the man who claimed to own half of Facebook and who has now been charged with criminal conduct.
The claim seems to rely at least in part on an alleged violation of Rule 3.3. DLA Piper was one of Ceglia's firms before it withdrew. Facebook claims Ceglia's "contract" with Zuckerberg was fraudulent.
I suppose the legal basis for any suit will be malicious prosecution or abuse of process or equivalent tort and allege that the firms knew (or should have known?) that the suit was a fraud. The alleged rule violation (which requires knowledge) would then be evidence in support of the legal claim. The Fortune story is here: