Man, you leave the computer for five minutes, and you miss all of the exciting news!
Apparently, Shepard Fairey, whom is currently in legal maneuver with my longtime "friends" at the Associated Press, has accused another artist of ripping off his work.
Fortunately for all of us, my lawyerly friends were right on top of this story. Since I don't actually have any knowledge to add to this story (unless one counts hot air and bluster as "knowledge"), I'll defer to Ye Kind Gents for the details:
Peter "Super Lawyer" Friedman says, in a nutshell, that it appears to be sufficient Parody.
Ron "Internet Superhero" Coleman adds his own avant-garde Oy vey—Which, near as I can tell, is not a Trademarked expression.
And I do nothing more than toss out once again that Fairey isn't exactly known for creating original artwork.
Please do be sure to click over and read what these fellows have to say. The murkiness of modern Copyright law really does have to be seen in action in order for one to gain a full appreciation for life.