Ever since it was discovered, and somewhat simple to do. Kids will try and get back at owners and moderators by Attacking them.
It being one of the only ways to attack a server (the Amateur way) i wouldn't be surprised if it was the first thing found on google "How to stop a server" or something of the sort. Peerblock was a good find, if it works i suggest anyone use it until ISP's can figure something out about this. (If they can, my Degree isn't in Networking. However, any protection is better then none)