GameKnot administration, in an effort to avoid people cheating, will err on the wrong side of caution. A situation arose where a coworker and I were logging in from our work site, and GameKnot admins made the assumption that we were the same individual. Because my coworker was slow-playing his winning games, they decided to ban his account(because he was playing slowly so his rating would decrease). Not only was he a lifetime paid member, but they also decided to ban my account because I might be the same person. I blogged about the experience here: https://richgautier.com/2007/01/locked-out.asp
While I liked playing at GameKnot and was a member of a team, I found my account stripped from me for no good reason. The administration fails to even answer my emails.
Advantages of the site include downloadable PGN files of all your games, a game move database for highly rated players, tournaments, teams, club/forums and a useful user interface. GameKnot is meant for slower play(days between moves).