A friend of mine recently had a bad experience with GameKnot. It looks like they have instituted an anti-cheating program and have hit on some false positives. They have a policy of closing your account, (paid or not) without warning, if you are suspected of cheating.
Aside from if their EULA allows from this, this isn’t how anyone should be treated if they pay or if a company wants a customer to become a paying member. If someone cheats, or looks like they are cheating, they should get a warning and be given an opportunity to deal with it. It is a matter of playground fairness.
Or play against the machine. They fight fair.