As you all know very well, seeding takes time, spreading an idea virally might require weeks if not even months. This is why Warner Bros has decided to start talking about the new Batman movie almost six months before its official release in theatres...
I actually arrive a few days later on this campaign, but on the Catch up Lady blog you can read an extensive recap of the integrated (online & offline) action to start spreading the word about Batman: The Dark Knight. Yes, because one of the most interesting things about the campaign is the use of outdoor advertising to drive traffic to the teaser sites.
Also, as you can see from the screenshot above, the teaser site has been actively online only for a few days... Today if you visit it you find an error page which actually "hides" a message from the Joker.