You know all those posts on message boards you run across that are about some new band that totally rulez!!! They'll have a link to a YouTube video or MySpace page or tell you how to download the band's ringtones, usually.
In the European Union, that practice will become illegal. Pop Justice posted an item last Friday about a new EU law that is to take effect later this month that would make it illegal to create an online identity for marketing purposes.
Surely created in response to high-profile cases like the CEO of Whole Foods going on message boards to talk up his company's stock under a pseudonym or The New Republic writer Lee Siegel creating an identity to attack critics and talk up his own genius, the law would still outlaw PR companies from doing the same to promote their clients, as long as they represent themselves as consumers.
Here's a good summary of the law.
At least in Europe, to shamelessly promote ones own band, publicists will have to go about it the old-fashion way: by getting "street teams" to spam online polls.