They can certainly sue. Whether they get any money as the result of the suit is another matter. IIRC, this was a question on Bergeron's Hollywood Squares. Forgot the source, but he said the most common password used for computers was PASSWORD. There wasn't a whole big argument about it either, but yeah, it didn't cost anyone over a half-million dollars. Chalk up another win for the lawyers.
The people suing might be hoping that they'll get a settlement to make them shut up and go away.