Most of his works have been moved or destroyed, I think. He's had works washed off, he's had works vandalized, the walls where a work resided has been broken out and then the wall has been sold to collectors.

He spray painted a piece onto plywood at a charity Boys Club, confirmed with the people running the club that the work belonged to them, so they removed it and eventually sold it for a pretty penny to keep the club running.

That dynamic seems to have always been present. I'm seeing some people saying he even may have etched the wall first, so I'm not sure. But with stuff like this you have to assume it was the artist's intention. This is what artists spend all their time thinking about and discussing! In art school even, beginner students are made to critique every line and mark of each others work. Any single piece of art itself is a conversation with the history of art. We aren't used to thinking like that, we think of art works as commodities with a dollar value. I promise you, banksy does not think that way