This thread grew like wildfire! My friend told me a while ago that Megan said something or other in an interview, basically saying she knew she was in there for eye candy. I think she was implying that the role or movie wasn't the most desirable for an aspiring actor, and the director Michael Bay got wind of it, and was none too pleased.
On a related note, maybe a week ago or something, I heard a thing on NPR about how Charlie Sheen in his sitcom asking for so much money, and experts chimed in with the history of rehires vs fires, and the related success of the show. They mentioned, IIRC, Shelley Long being replaced by Kirstie Alley in Cheers (and yep still successful), and I think maybe it was the husband in I Dream of Jeannie, but anyways I believe it was a major role, and the show did just fine. Ok, a google shows that Sheen got his lucrative contract after all . . .