Like Hrnchamd mentioned, for everyone getting all excited, let's dissect this sentence:
It doesnt matter what computer you have because the game is played on their servers and streamed back to your screen, making your monitor the only relevant thing you own.
Have you ever used remote desktoping, VNC or a similar solution? More importantly, have you ever measured the response times? And have you ever run it over a long-distance internet connection?
Now, the last time I used this, logging into my home server using a hard-wired 100mbit connection (roughly 10x the top speed of cable internet) that only went through a switch on the way, I got something like 5-10 FPS in 16-bit, with compression and a few other optimizations (VNC, Ubuntu to 7). The systems in question were 2 GHz and 3.4 GHz and had hundred megabit LAN ports. I used about 3 feet of CAT5 cable.
I've also used and seen quite a few internet surveillance systems, most of which use black-and-white or low-color images and send 4-8 a second. Even at that rate, they still lag.
The implications for that mean that going over the internet (which tends more toward 5-8mbits, on a good day I can get ~14) you'll be lucky to get more than 10 FPS in low color. Unless they can set up a super-optimized system with VPN tunnels and a custom server/client streaming method, it's going to be
slow.
The real killer? Input. Even over a close-range remote desktop, there's an input lag. When we combine the 1/10-1/2 second video lag from streaming with the
returning 1/10 second input lag, it may be up to a second from the time the enemy should have appeared to the time you swing. As anyone who has ever played a shooter knows, you can be good-n-dead in that second. Even in Morrowind, at low level with a Golden Saint running towards you, that second is the difference between turning and making it 10 feet or being cut down where you stand.
No matter how they do this, it's gonna lag like a [censored], and that's gonna be a game-killer.
Now for the technical side, they'll need, oh... a computer for each player. If this ever picked up, server-farms wouldn't be cutting it anymore. Servers aren't designed to do the kind of rapid graphics computing and AI processing, they're data storage and retrieval systems. They'll need, at the very least, a number of quad-core quad-processor servers with multiple Tesla cores in each to be able to even start to handle any kind of load. If they want to serve new games, even things like FEAR2 or Red Faction Guerrilla, they may need dedicated systems for each subscriber. Imagine how the prices will go up when they realize that.
The bottom line is you're much, much better of playing the $1800 for a solid gaming desktop and using it at home with no lag than you'll ever be spending a few hundred a month to pay someone else to buy it for you.