Personally I am a huge fan of Banksy. His frequently situationist approach appeals to my rather simplistic view of art (hence my continued love affair with the work of Drummond and Cauty despite their long distant fall from grace). A good prank is a good prank as far as I’m concerned, and it’s hard to see what else there is left in current artistic endeavour. If we no longer care about skill in execution then comedy and shock are all we’ve got left.
Personally I reckon if you live by the sword, you die by the sword. His work (or at least his graffiti and his pranks) are by their very nature impermanent. Like smallpox and pandas their time will eventually come, and we should accept it. You can try and preserve them if you like, but let’s not get hung up about it if they pass.