It's like that futurama episode when Farnsworth makes all the robots exhaust at the same time from easter island.

They brought this up in some movie or TV show, but I can't remember what or where.

I doubt it'd work, but it was good for a laugh :)

Sounds like a major earthquake waiting to happen.

Unfortunately, the physics behind the jump theory are flawed.

Due to Newton's second law (For every action is an equal and opposite reaction), the gravitational pull bringing people back to earth would bring the earth back to people.
Anyways, even assuming everyone in the world participated, the earth would be back in it's original orbit as soon as the last person landed back on the ground.

The only way to actually change the earth's orbit through action/reaction would be to actually jettison material from earth, like a giant fart.