I have never been into the documentary genre, but from time to time I will check one out. You rarely hear about them in the theater, so DVD and online video is pretty much the best way to go. Once they get nominated for an award it then becomes the trendy thing to talk about, which is lame because if you didn't care about it before why do you all of a sudden have to talk about it like you are some cool person that knows more than the next person about movies.
Anyways, "Exit Through the Gift Shop" is about this French guy, Thierry Guetta, who set out to find a reclusive graffiti artist named Banksy. He hides his identify throughout to protect himself from prosecution. I don't know that i have ever seen any of his work, but there is something about a quality graffiti job compared to simply tagging that is considered "art" in my mind. so Thierry eventually locates Banksy and convinces him to let him film some of his exploits so as to compile the footage into a documentary.
The audience, as well as Banksy, quickly realize that Thierry isn't much of a film maker and just someone with mental problems that just happened to have a camera. So Banksy takes the existing footage and turns the camera on Thierry, who has now decided that he too will take his turn at being a street artist under the moniker Mr. Brainwash (MBW). This is when the best parts of the documentary start to come out, because it is clear that Banksy is more than just a graffiti artist, but rather he has the artistic ability to extend himself into other mediums (including film).
A question that is often debated is "what is art?" and my response to that is that you know it when you see it. That may not be the answer people want to hear when they ask the question, but it is true because Art to one person may not be so to another. When Thierry sets out to be a street artist there is nothing different about what he is doing as compared to what Banksy is doing, however because there is no one like Thierry that is what makes it art nevertheless. Ultimately, there are no real rules in art and that is what makes art what it is.
If I owned a building and someone put graffiti on a wall of the building that was artfully done then I would be okay with it. It is vastly different from tagging. Documentary is still not my preferred choice, but it was a great way to spend an evening when nothing was on TV. So I give this one 2 Quacks.