This was also a common tactic in Tribes, which also had jet packs and 'skiing' (basically bunny hopping downhill while building up momentum). The game had vehicles, but after people figured out skiing, the vehicles were basically abandoned.

In the later years of the game, people even figured out disc jumping in midair off of their own grenade.

Edit: here's a quick Tribes 1 video where a guy skis around the enemy base, team kills his own flag carrier, catches the flag in midair, and disc jumps home to cap it.

http://youtu.be/HF_htZRhbiQ