Well how about this...
After a certain point, wins don't give you any rating points.
ie. You consistently play 1400's at a 1600's strength and beat them every time. You gradually work your way up to 1900 ... after you are 500 points stronger than your opponent, a win gives you no points. This way it's not possible to achieve rediculously high ratings simply by playing a huge volume of lower rated players.
Simple, easy to fix... the only drawback is that it may not be 100% effective... it will always be possible to be 400 points or so higher than your genuine strength.
OPTION #2
Create a huge site championship annually and make everyone play in it...
I don't even need to state the problems here, it might work though...
Does anyone have suggestions on improving stats? :)