Just cut a ~50' tree yesterday, the back cut was a smidge low on the far side and caused it to spin a little, catching another (standing dead) tree on the way down. The force of the felled tree sort of 'cocked' the dead tree back away from me and it hung up. I cut a few strands of the hinge, which let the tree roll back off of the dead one it was hung up on, but when it did so that dead tree *snapped* back at me hard. If any of those top limbs were loose (either naturally or from being struck by the tree) it could have *easily* made it to me, if not twice past me.
Sometimes you learn just as much from the could-have-beens.
Edit: OSHA has a pretty nice site for info on cutting trees:
Logging eTool: Mainpage