Movie studios wary of Netflix are looking at another possible alternative to the dominant video rental service: Facebook. In a Warner Bros. "experiment," the studio has decided to make the highest grossing movie of 2008, The Dark Knight, available as a digital rental on the social networking service. Warners tells the Hollywood Reporter it's the first studio to offer movies directly on the site.

To watch the title, navigate to Knight's fan page, click the "watch" button and it will charge you $3 dollars worth of Facebook credits for the rental. Since the Facebook interface is so familiar, it's all quite intuitive.

If enough people decide to watch the Batman title one more time, Warner and other studios will presumably upload more of their movies to the site for rental--and, if they're lucky, they might be able to cut out Netflix as a distributor and keep the full profit (note: it's unclear if Facebook will receive any of the rental revenue) themselves. This would be a blow to Netflix, Amazon Prime and Apple's iTunes stores, which all have deals with studios in place to offer streaming "on demand" content.

Warner's Facebook experiment raises a simple question: what took the studios so long? All Things Digital's Peter Kafka noted this and observed, "Facebook is either the 2nd or 6th-biggest video site in the U.S., depending on who’s counting. And that’s without the benefit of any Hollywood hook-up at all: Just the clips you and your pals put up." Naturally, Hollywood is hard at work trying to monetize all those two-minute movie clips also.