Thanks go to Woolfman for the info:
It happens that they were in the classroom scene that was being shot yesterday with Rainn Wilson. The shoot was to cover two separate days within the movie, the first day of classes for Sam, and the second day of class.
The reason we suspect that it is an object he touches that makes him crazy is because there was a scene shot earlier where he was on the phone Fox’s character Mikaela, and he was asking her if she had “it” and then told her to make sure she doesn’t touch “it”. Our guess is the “splinter” (left over piece of the Allspark Cube), but it could be something else, of course.
Oh, and the last scene that was filmed on Wednesday evening was of Sam arriving to class while riding the red motorcycle that people have seen in pictures. I don’t think that proves whether or not it is a Transformer or just a motorcycle, but it could be worthwhile information in the future.
My guess is that it would be a piece of the All Spark that Sam kept after thrusting it into Megatron. That would explain why Optimus Prime thought there was nothing left of the All Spark at the end of the flick.