It's a contradiction in terms. When once the work was about making a political statement about society and government and being made by subterfuge it's now a part of consumerist society and an augmented reality surrounding that than it is about the piece in itself.
The intangibility which makes Banksy's art become a work of art is non-ownership so that the pieces don't have a financial value. The value is in the experience of witnessing them. But theft and removal from their unique physical position is giving it an ever-increasing sales value on essentially the black market. Non-owners are making themselves owners through theft and profiteering and taking way the actual value of the piece, it's intangibility, but making it a tangible object. But as wealth and ownership are falsely engineered values and the new 'owners' take possession through wealth, is this doing away with the value that they think they have in the piece they have bought? Banksy himself said:
"Despite what they say graffiti is not the lowest form of art... There is no elitism or hype, it exhibits on the best walls a town has to offer and nobody is put off by the price of admission"
So maybe Banksy can't be right any more. If his work can't be viewed by the public, and only the elite take ownership, then is it no longer art when it doesn't communicate what you intended it to to the audience you intended to view it? How much new art is Banksy able to make due to his work being elevated out of his control.
By aiming to make low art become high art, maybe the profit being made by non-owners and councils alike is stopping the art from being art.