"There would also have been hundreds of scheduled passenger and frieght flights in the area. Wouldn't MH370 have shown up on any of their radars, possibly as an unidentified flight? Wouldn't the pilots of any of those scheduled flights have reported this anomaly that they were seeing on their radar to air traffic controllers?"
I'm just trying to clarify - are you suggesting that the other aircraft carry radar that can see other aircraft in the area?
If so, I'm sorry but that's not the case. The only true radar carried by an airliner is a weather radar. It has something called TCAS (Traffic-alert and Collision Avoidance System) that makes the pilot aware of other aircraft around him or her but it doesn't give the info that a true radar would and is really only there to avoid collisions (does what it says on the tin!)