Well, not making a profit, so much as remaining afloat. After all, Movie Mistakes has been running on pretty much the same basis as the IMCDb for years, with timecodes and screenshots and contibutions spanning film history, and I don't think they've ever had legal problems. The people who run it are also quite restless, coming up with all sorts of creative ways of expanding the site and displaying the mistakes. In the past few years they've added a Book Mistakes offshoot, a list of supposedly 'perfect' films, sections devoted to easter eggs and quotations, and even a few illustrative YouTube videos. This goes back to what I was saying about the need for an exhaustive database: the tiniest, most unexpected bits of data could cause you to notice odd things that grow into richer content for paying members. For example, anomalies such as cars in disguise (the Renault Alpine in Eldorado turning into Triumph TR7 before it explodes; the Aston Martin DB4 in The Italian Job suddenly becoming a Lancia Appia for the second take of its plunge into the gorge; the Buick Riviera with Jeep Cherokee instruments in Red Rock West) or some timeline feature where you pinpoint the first time a particular car appeared onscreen (just looking at the Reliant page, it's amazing to see how Regals were acceptable background vehicles in the seventies, before suddenly beoming a figure of fun in Only Fools And Horses. There's a feature in that, surely?). Coming up with interesting ways to use this exhaustive resource shouldn't be too difficult, or illegal. Since cars and films are both pretty broad in their appeal, there could be loads of takers. The memberships would fund all these excursions into presentation, which would attract more members, and so on.

EDIT: Damn, I should really have refreshed before posting all that. Do you not think, antp, that any distinctions as to what contitutes a film 'rôle' would end up being arbitrary and unnecessary? Maybe those who would rather not see pages of background vehicles could have an option to turn off one-star-rated cars?