In a statement Banksy, his dealer Steve Lazarides, and the directors of POW, confirmed that unauthorised prints "have been sold on eBay" and stressed that they along with members of the public "have been victims of criminal behaviour". The company has launched a full-scale investigation and is inviting concerned collectors wanting to reauthenticate their Banksy prints to come forward," says The Art Newspaper.
I don't know about you, but this really makes me worry. It seems that everything is fair game to be stolen and sold on Ebay by anyone unlawful enough to try it. Another reason why it is important to Google your name and works at least once a month to see where it pops up on the net.
I do this quite often and have found several of my written works plagiarized. I promptly contact the person and threaten legal action if they do not cease and desist. I have actually had a hand in putting a plagiarizing website out of business by spreading the word on forums and newsletters about their practices, so don't think there is nothing you can do to stop these people who steal work.
Alina