Needless to say, Bruce, the filmmaker, and everyone else behind the film deny there's anything fictional about it. Interestingly, the distributing team - Court TV and Wellspring - has refused to use the simmering controversy as a tool to promote the film. Given the marketing potential in a "Is it or isn't it?" campaign, it would be a move of incredible stupidity not to use that angle to promote a film that you know is faked and, presumably, plan to eventually come clean about. That, combined with the fact that not a single shred of concrete evidence has surfaced to disprove the reality of the film, seems to suggest that UWM is telling the truth. After all, as JT Leroy and James Frey can tell us, it's almost impossible to keep a secret this big in the modern world - you've got to believe that something would have leaked out by now.
That said, if it's a hoax, it's a fantastic one, and I'm just one of the many suckers.