Frank Zappa released Lother album free to public via radio broadcast to show his independency from the record companies that tried to screw him up. Every artist has a right to perform their own music regardless of contracts with recording companies. Free album distribution via iTunes will only uplift their rating(regardless what anyone here thinks about U2 likes-dislikes or similar opinions) and increase size of their audiences when they book a tour. From the artist standpoint, when everyone's sharing digital files legally and illegally it's a smart choice and as I mentioned before, they're not the first and not the last to make that move.