Here's two non adult sites that have never been penalized for being in such networks:
http://www.scam.com
http://www.dirtfiles.com
They have been in similiar link exchange systems along with thousands of other reputable sites for over a year now. The companies that get in trouble are the ones that use google's logo and make promises. We do no such thing, even though people KNOW what they KNOW....ya know?
....it all goes without saying...so why say it?