Freelance ad guy S. Tristan Hartley (who left the high life as Bozell's Interactive Technology Director to return to the good life in Omaha NE) emailed in his current experience on the bad-names-in-b2c-"opt-in"-email-lists front:"I've built several mail campaign management centers allowing my clients to send/manage/track their email campaigns. I started banning rented lists about 9 month ago. I have a similar policy to Ben, shutting their accounts down, yet a couple clients still try to sneak them by. Personally, other than my philosophical beliefs completely 100% against spam being compromised by association, I don't get burned by them doing it as I go the extra step of putting each clients mail center behind its own domain with them listed as all but the technical contact. Thus resulting in them dealing with all the blacklist problems and complaints.
But I can definitely tell when a rented list has been used. Complaints easily run 15 - 1 versus an opt-in list (and the 15 - 1 ratio is conservative!!!)
To get around my shut down policy, I've seen clients hire temps to transcribe rented list addresses into their web-based personal address book or manually enter them through their opt-in sign-up form and even having a new hires claim that it is "his/her personal contact list" from a previous job. It is quite interesting to give them a lesson in reading a log file or showing them the datestamps on each record in the database--you had 60 sign-ups an hour for 8 hours a day the last 15 business days straight...hahaha.
Also, The Story of Nadine also hit home. I have one address on sh2.com that someone from the domain sh3.com mistakenly entered (which has been confirmed). That was about 3 years ago and today that address receives about 8 mails a day, some of which are even from 'reputable' marketers."