In my limited experience with new riders the greatest problem is that people forget they're on a large, heavy, powerful machine and try to muscle the motorcycle like it was a bicycle. They push with their arms, try to stop with their legs, and drag their feet. They think they can stop or propel the bike with their body while not considering it weighs 3-4 times as much as they do and has considerably more power.
Mopeds, scooters and vespas are much smaller and can be muscled to some degree. This isn't to say they are less dangerous on the road but they certainly aren't as unwieldy like the big bikes.
My girlfriend screwed up in the MSF course on her 250 nighthawk and went straight over the bars and onto her back! It was a hard lesson to learn but the bruises healed and only the bike controls were busted.
