I think that was my only big problem with the film. Sam pushing the AllSpark into Megatron’s chest was a great ending for TFilm1,but it doesn’t seem to work well in the long-term. Look what has happened to Megatron in consequence: he got degraded into the role of supporting villain to the big bad (the Fallen, Sentinel Prime). In ROTF he got rebuilt as the Fallen’s servant. While I think lots of fans miss the fact that G1 Megatron was similarly revived as Unicron’s servant Galvatron, I agree that Megatron didn’t deserve that fate – he’s Megatron, he is apprentice or disciple to no one! In DOTM he got a little more respect, as a broken-down leader who gets deposed, and then finally decides to take back what is his (it was ironic that the last ten minutes or so – the time when Carly provokes him - he was like himself in the first film again). Giving each film a separate antagonist may keep the series fresh (and to some degree it keeps the films self-contained so you don’t have to rely on watching the others), but it distracts from the fact that Megatron is THE main villain of the TF saga. That’s how it is, and how it should be.