Instagram, an artist and the $100,000 selfies – appropriation in the digital age

Richard Prince has turned borrowing online images into high art - and hard cash. But is the artist's work anything other than genius trolling?

It's a question as old as art itself: "Yeah, but is it art?"

Type it into Google and get 1.26 billion results. It lends itself to book titles, television series and conversations between white walls, whetted by prosecco.