Hey, can you register the same Kindle (i.e. same serial number) on 2 different Amazon accounts? If not, then there's an easy solution. Create a new Amazon account and switch to that one, then remove all billing and credit card info on your old account but leave the registration info there.
Download all the ebooks from your old account and transfer it via USB to your new Kindle, and voila, that fella can't register your lost Kindle and hence can't read Kindle books...
