KMageau is dead wrong - thousands of people already do this on a regular basis. They're called MUDs and MUSHes (among other squishy-sounding names) and they range from places with coded combat like a text Everquest to free-form statless roleplay.
That said, I don't think you'd have a lot of crossover for a web-based game - it would lack the player interaction of the telnet-based MU*s, which is a large part of the attraction (that and the fact that the code is open source, letting anyone who wants to run a server.)
To succeed as a web-based game, you'd have to have a definite 'hook'. Kingdom of Loathing has this with its intentionally crappy graphics and wonky sense of humor, but it looks like you're going for a more 'serious' game.
J