If you don’t want to bother reading the article, the one word is: hashes. The RIAA claim to have a database of MP3 hashes dating back to files traded on Napster. Sounds like the easy way around this is to simply wipe and recreate ID3 tags on all your MP3s, as that will certainly change the hash of the overall file. I think the problem with this will be that “swarming” (multiple sourced downloads) may not work if the file hashes are different. With DSL and cable modems so widespread now, though, it may not matter as much as it would have a couple of years ago. I wonder if a facility to refresh ID3 tags will appear in upcoming versions of file-sharing clients?