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As MadMonkey said, there are many games which 3-4 player games would be very very very very very cool!
It would take some extra programming work by Fencer, but I would not think it would be too hard. (The hardest part might be trying to figure out how the ratings are calculated).
Time outs - for some games like chess, that would be hard since what do you do with the timed-out users pieces. Do you end the game for everyone (The people who did not time out co-winners) - what if player 3 is in a very good attack position towards player 4 - but player 3 times out - do their pieces stay on the board (limiting player 4), are they removed, which hurts player 2 since he was "attacking player 3 and now his pieces are not in a very good position", etc.....
But other games would be perfect for 3-4 players - Dice poker, boats, etc... And my favorite - the game that WAS MADE to be played with 3-4 players, Frog Finder.
I'm sure it would take a lot of work to get it made, but having the ability to play games between 3-4 players would be very cool.
As for the ratings - that is where it can get tricky - since many times, the game is played totally different between 2 players and between 3-4 players. I know other sites just clump all the ratings together.... which at that point, some avoid the 3-4 player games since it hurts their ratings too bad. Maybe a way to have 3 ratings for 1 games.