I was watching my Transformers Trilogy blu-ray set (which is awesome!) yesterday and flipped through the DOTM special features. In it are a bunch of stills featuring new production art from the film. One of the most notable images was that of the large spider-like Decepticon featured once or twice in the Chicago scenes of Dark of the Moon. The working name for this elusive Decepticon is Devcon, who used to be an Autobot in the G1 mythos.
Anyway I just thought it was cool and one more mystery solved!