Discovered by the Transformers fansite TFormers.com, the poster is quite similar to the first teaser poster for Transformers: Revenge of the Fallen, which simply had the tagline “Revenge is Coming.” Although this poster does not bare the title: Transformers The Dark of the Moon, it does look quite genuine.
Update: Michael Bay has spoken from his official site and stated this is a "total fake poster, the logline is also a mis-direct" Oh well nice try.
