Detecting exceptions and fraud on recommender systems

I stumbled across this iLike profile when I noticed someone who'd listened to David Bowie over 2 billion times. "Patrick S" has, according to his profile, been alive less than a billion seconds (and iTunes has been available for only the later part of his life), yet he's managed to register over 2 billion plays for 32 separate artists. The data concerned seems to be imported by iLike from iTunes.

Who knows whether this is just idle mischief, a software glitch, or a concerted effort at gaming or 'shilling' the iLike recommender system? Whatever the cause, recommender systems clearly have to detect such incongruent profiles — which can't be hard in cases as gross as this — and make sure the data is excluded from their recommendation algorithms. Cleaning up the profiles for this user and the 32 artists concerned would be a good idea, too, lest they undermine others' confidence in what they see on the site.