They do police it to some extent. I have been stopped from entering a 1 tbl sng and cash games because my cousin was registered or sitting at the same game and we were on the same IP address on my home network. I have also seen tnem catch IM between players. Fact is they cant stop it entirely but they do seem to try as best they can. Its the risk we take to play the game we love... or in some cases manicly obsess over.