I asked: "What's your policy on the artist/album information you collect (when SL scans a user's iTunes, for example)?"
Answer: "We only track artists (not album info). For the time being when you remove an artist from your Wishlist, the info is permanently erased and no record is retained. In the near future we will begin tracking artists that have been removed so that we don't re-add artists when folks rescan their iTunes/ Pandora/last.Fm."
Hat-tip to a privacy guru who motivated me to find out, and kudos to Elle at SL for her clear and prompt response. My next feedback will ask them to post their policies!
UPDATE: Elle says they are working on getting their policies finalized and posted ASAP.