Bandwidth due to the more "twitch" nature of the game. MMO's run off of basic actions that are lined in a que. It limits bandwidth issues.

A racing game requires constant input. Thats where the bandwidth issues come in.

The idea is for the city to be very big. VERY BIG.

Does it mean that there is no possibility of traffic jams...no, but a large city could very well work out.

Non-instanced races...yes the idea of interferrance is there. Its part of the idea.

How would a MMO not need constant input as well though?
I mean, don't you need to know that if your friend is pushing up he is going foreward?

or, if your friend is under a "poison attack" that his health will drop X points every X seconds?

Or how about the fact that if there is A trade going on...will you not have to see what is being traded?

The only way around this I can think of is that all your data is sent to a higher speed database, and then downloaded by everyone in the X square mile/foot/yard/etc.

Because in an RPG style MMO, Lag won't affect what happens as much. You don't have to worry about constantly adjusting you're movements. Lag won't affect you as much as it will ina racing game.

Yes there is constant inputs, but the game can make certain adjustments and assumptions when there is lag.

Thats why you see auto attack instead of Zelda like controls.

With enduro races, the tracks are small enough that a lap lasts about fifteen seconds. The last enduro race I watched was two hours long and half of it was due to red flags. I like the MMO idea for this because you could start with a basic car and purchase upgrades and customize the car, though it might not work as well for this type of game as for others.

I agree that a pure racing MMO is barely viable - but, if part of a greater whole it is definitely ripe for being in an MMO.

Im going to shamelessly pimp my own project: CONFLICT: Omega because it actually fits the subject. In our game players can find cars, salvage parts to upgrade them, then use them not only for combat or travel, but our hopes are thatwith a little prodding a racing community will spring up.

Again I dont think racing gameplay is worthy of its own MMO because there's no role to play....not much interesting to do in the downtime between races.

Perphaps if you treated it like a simulation game and took a console-type "career mode" and "manager mode" and set up a situation where players both adjusted the stats of their drivers and cars based on skill points won through races you might have a start. Add in some sort of business sim where you had to manage various factors of the company...and then put that in a persistant world...you might have something there.