Interesting point here from Reason on the leaked Marvel Age of Ultron trailer:
The trailer wasn’t supposed to be released this week at all. Marvel had originally planned to release the trailer next Tuesday, in conjunction with a new episode of Agents of S.H.I.E.L.D, a TV show with close ties to Marvel’s ever-expanding Avengers movie universe. After a low-resolution version of the trailer leaked, some copies were pulled at the request of Disney, which owns Marvel.
…within about two hours of the leaked version hitting the web, Marvel went ahead and posted the official version. So much for carefully stage-managed corporate PR, eh? But this is one of the reasons why Marvel is doing such great business these days. They’re not fighting the fans, not trying to control the crowd. The company is accepting the reality of the Internet—that a leak can’t really be contained—and giving fans what they want.