I noticed a cached backlink coming from a weird page, so I paid it a visit, and look what I found http://www.fridayfoofah.com/books/foofbacklogstudies/backlogstudies116foof.php
google doesn't have that page, or almost anything else on that site in it's index anymore, so I probably wouldn't worry about it.. it's not benefitting from the ad network
Which would create the possibility that all coop members are linking to this possibly blacklisted site, doesn't sound like anything to worry about to me...
1) it's likely they tried to use this site to create weight to send elsewhere. I can almost guarantee you this isn't the site they're trying to promote 2) because it's blacklisted, they're not getting any weight to spend.. ads in the network aren't ever showing ads as a result of that page.
That's one of Rick Bender's sites. That's where the $49 10K links deal is on (amongst others). Ugly but no harm to network members.