Of course, even if this isn't true, it could happen; it could be one directive from head office or bad "war on piracy" law away. As such, if you're listening to anything you could be prosecuted for the possession of, turn off your last.fm scrobbler. Or set it to a different account with the identity of the CEO of the RIAA or something. (Hypothetically speaking, of course; The Null Device does not condone identity theft, or, for that matter, listening to U2.)
I wonder how long until some hacktivist writes a bot that is fed with the track listings of unreleased recordings and, when run by a user, automatically reports to last.fm that the tracks had been listened to as an act of anonymous protest. After all, they can't raid everyone, can they; and the existence of such a bot would make the "evidence" useless for prosecution or search warrants.
As the brother of someone who has been obsessed with the comings and goings of one Paul Hewson and friends since Rattle and Hum tried to kill the Blues, I can tell you that the lively trade in secret pre-release U2 albums online is pretty much the only thing keeping the band alive. The RIAA are really shooting themselves in the foot with this one.