Movie studios have had a gutsful of leaks on Twitter and Facebook and are adding new rules to its contracts forbidding actors and other creatives from blabbing on the social notworking sites.

DreamWorks and Disney are the first studios to clamp down on tweeting. Cameron Diaz and Mike Myers among the first to be affected when they film the upcoming Shrek sequel. Celebrities have been big fans of social media because it allows them to broadcast their thoughts directly without being filtered by journalists.

But the lack of control over their stars is causing Hollywood execs to panic. Paula Abdul recently surprised her Fox bosses by revealing through a tweet that she was leaving American Idol.  Heroes star Greg Gunberg published a message that led some wrongly to believe that the show was being canned.

Hollywood has a long tradition of telling its starts what they can say. It starts with a script and ends up with long PR events and speeches.