I went to www.whois.sc, and checked one of my domains. When the whois record shows up, there's a part on there that says "Registrant Search: XXXX XXXXXXX (XXXXX@XXXXXXXX.XXX) owns at least 2 other domains". My name and email is there. When i click on the "2 other domains", it says you can buy the report for $57, and see what other domains i own. Are there any other sites that do this?
Yes, theres also sites that show you past domain history of users, dates at which they bought and sold etc. It sucks but its been going on for a while, and thankfully not that many buyers look you up.
I think you're talking about the http://www.registrantsearch.com/ ads that appear on whois.sc site, If you are more concern about privacy better protect your domain info by making it private.