Or subspace! http://en.wikipedia.org/wiki/SubSpace_(video_game)

It still exists as Continuum -> http://www.getcontinuum.com/

From the website: Ever imagine what it'd be like to play Asteroids against your friends?

Subspace is exactly what I had in mind when I saw the OP. It even has a bot API, though unfortunately no one has made a fully-playable one yet.

May I plug my own game here? It's not multiplayer but still favor intense dog-fighting with AI.

http://gamesfrommars.fr/vibrant

A multiplayer mode is the most requested feature, but I don't know if it's worth it.

That game is evil. It ate at least two startup's worth of productivity from me.

this is one of my all-time favorite games.