I don't know, maybe he is a vandal; he's certainly not in the habit of asking permission, pretty-please may I, before graffiting. On the other hand, after he has struck, the property-owner (if any!) is left with a genuine Banksy, and his work does have some bank. He's something akin to the fellow who drives by your home and throws a bag of gold coins -- through the window glass.
The artist has spent a month or so in New York City. No matter what you might think of the man, his art, or the manner in which he practices it, his work is most definitely art and keenly-observed art at that. Sure, he's got good technical chops, but so does the guy who paints vignettes on vans down at the auto-body. Nope, IMO what makes it art is the application of those skills to depict visions like a robot executing the exact kind of tagging you'd expect a robot to do (if you'd thought of it first), in a world where, after all, objects are so tagged, and indeed read by robots. Or to see a bricked-up arch as a Japanese bridge and get you to see it, too.
I enjoy the backhanded beneficence of creating these things and just leaving them-- It is a kind of meta-advertising (and here I am, participating in it) that exploits and subverts traditional channels of information; reflecting his art in a holographic way, it, too, is carefully-observed and deftly used.
And perhaps that's it, the bit that goes beyond technical skill or artistic eye and judgement: his work as a whole is something of a well-played magic act, complete with the mystery of what he might be up to next and how will he accomplish it.
5 months ago