That is crazy! Would there be any benefit distributing your files with a disclaimer(like a word file)? While that does not prevent them from doing what they do it does add give you more legal weight.
Virtually everything is ripped-off in one way or another: software, 3d models etc. And its guys like us that get undercut when that happens, CGT does have disclaimers and to a certain degree we are protected but this kind of behavior can not truly be prevented.
I understand it may be a lot of paperwork to retract the models on EBay, but perhaps therein lies the opportunity: Sell you own models on Ebay! This fraudster obviously makes money off of it. You could alternatively offer him a royalty agreement whereby you make a percentage off of all the models he sells on there. These aren't necessarily safeguards but they my be options that can benefit you.
Let us know how it goes.
