This is nothing to do with the quality of the film. I haven't seen it, so I can't, and won't, comment. It's about the subject matter. It would have made me very angry, and I'd have left the cinema seething. I'm not sure if that was the emotional response they were after.
From what I can tell, the movie goes like this. A guy, Thierry Guetta, decides to make a movie about street art. Guetta shows his footage to Banksy, who tells him it's absolutely terrible, and suggests that he should try his hand at painting instead, while he (Banksy), despite having no film experience, will edit the footage into something watchable and finish the movie. So Guetta goes off and makes a load of equally terrible art, hires a warehouse in LA, and tells everyone that Banksy told him to be an artist. He hypes it like crazy, and suddenly his stuff is cool and he's an instant millionaire and the darling of the LA art set. The film ends with an embarrassed Banksy saying "I used to think anyone could do art. Now, I don't think like that."
Now, it's very likely that this wasn't a genuine documentary. I'd guess that Banksy set the whole thing up, just to take the piss out of the art world. Either way, though, the message of the film is the same.
Being a successful artist has nothing at all to do with talent. You can be absolutely terrible, but if you have the support of someone famous, you too can get rich and famous. People will buy your art, not because they like it, or even because they think it's cool, but because they think that other people will think they're cool for having it.
Even if it's another spectacular hoax, it's an insult to every talented, hard-working artist I know who's trying to get noticed. Don't bother going to art school, kids. Don't bother perfecting your craft. Don't even try to be original. Just do any old shit and get someone cool to back you, and you'll have people fighting over your work. It's Malcolm MacLaren and the Sex Pistols all over again.
No, that's nothing new, I know that. It's always been that way, and I'm not in the least surprised. But I wouldn't have enjoyed sitting in a cinema for an hour and a half having it rubbed in my face that talent is completely worthless, and the only thing that counts is having a Banksy on your side.
Don't let me stop you watching it. All my friends loved it. It was certainly thought-provoking, even without having seen it. But given that I spend much of my life trying to promote talented artists, the film's message is not one I personally want to hear.