And, because the studios have a relationship with the toy companies and understand this part of the business, they generally don't have a problem with some minor spoilage coming out that way. It feeds into the media machine and drives more interest in the movie, after all, and how else are your business partners supposed to do their thing if they're forbidden from even displaying their own wares?
What seems to be something of a growing concern to studios is when spoilers are revealed not by the official toy images or announcements but by merchandising and licensing conventions, where concepts at an early stage in development are discussed months before the film's release.
It happened a while back with Man of Steel, with some information leaking that Warner Brothers insisted be taken down--and it's happened again, now with Iron Man 3, as Omelete has been asked to remove a fairly detailed summary of some information gleaned from Marvel’s president of worldwide licensing, Simon Philips, at an event in São Paulo.
The long and short of it is that there are minor spoilers for the movie he leaked, all of which have pretty intuitive ties to toys you might see coming in the next few months in support of the film.
At one point, apparently, Iron Man cobbles together a suit of armor made up from remnants of old (presumably destroyed) ones, so that he'll have bits and pieces of at least 16 different uniforms. This sounds like a third-act Hail Mary after the Extremis stuff stops working to us, but that's just an educated guess and not something that came from Omelete.
There's also been reports that at one point in the film Stark may shoot out of his car and have the Extremis-powered armor catch up with him along the way. That, too, would make for a great toy although it's not from this same report--and one wonders whether that was related to the high-speed chase scene that was filming in North Carolina early in shooting.
The last, and potentially biggest, piece of information is that Gwyneth Paltrow will reportedly finally get her turn in the armor as Pepper Potts dons the "Rescue" suit at some point in the movie. That's a rumor that's been persistent for a while, and we can probably call it confirmed to hear such a frequently-repeated bit of gossip coming out of the mouth of a Marvel executive.