They have your IP address. For those who don't know, an "anonymizer" site like NetShade will route your internet connections through their servers, which give a different internet address than your own. NetShade is a good company, if you decide to use an anonymizer make sure you do a "reviews" or ratings search on Google first. Some of them are NOT honest companies and can cause you problems.

Anyway if you use something like Netshade, they won't be able to ban you on the basis of IP address.