I was watching some stuff on Tribes: Ascend and was reminded of something I haven't seen in years. Emergent gameplay. Where something completely unplanned by a game developer becomes the norm. Not some exploit which the developers quickly stamp down on but those rare occasions where they step back and encourage it.
The Rocket Jump is the best known of these and emerged in Quake 1. Basically the rocket would create a lot of force throwing the player or enemy away from the blast. But the blast from a single rocket was not lethal. With armour and health boosts it could be reduced to a negligible level. So players found they could make their character jump, shoot a rocket at the ground underneath them, and fly up to a great height. The Quake series has stuck to allowing the rocket jump in all their games since as well as it persisting in Quake mods like Team Fortress which is now a standalone game with its sequel.
Tribes Skiing is the other example of an exploited physics engine. Tribes already let players fly briefly using jetpacks but clever players found rapidly pressing jump would let their character build up speed going down hills. And the rapid jumping would let them slide up the next hill where they could use the jetpack to aim to fly over and hit the next down slope. In the sequel (and all tribes games since) skiing has become an accepted part of the game and reduced to just holding down space bar rather than the old rapid tapping.
There's other old examples around but it's hard to find many that become the normal way of playing. You can't be considered a skilled player in Quake without mastering rocket jumping. And to play Tribes without skiing will earn abuse from your teammates. So scamming a MMO economy hardly compares.
So I wonder why it's a thing of the past. Was it just a brief time of buggy physics in games? Are developers more vigilant against apparent exploits?