think about it.. it does nothing for the autobots in either movie so far. in the first movie, it regenerated frenzy, but wouldn't do anything for bumblebee's voicebox. It transformed a bunch of electronics into evil, fully armed robots. and sure.. it killed megatron, but that wasn't its fault, it was sams. I think it originally influenced optimus to jam the cube in his OWN chest trying to kill him by making optimus commit suicide, but sam fucked it up and jammed it in megatrons chest instead. which brings us to the second movie. Again, the shards create life, but all the little bots are evil as fuck, and destroy everything in sight. Later the shards are used to bring Megatron and jetfire back online, obviously the transformers know this power of the allspark can regenerate bots no problem, but it doesn't do shit for optimus cuz he's not evil. He has to lay there dead untill sam figures out another way to bring him back online. farfetched?