Forum Moderators: martinibuster
I don't think one or two bad links will kill a site - after all, sites do get bought out or snatched due to expiration, etc. The more links to spammy sites you have, though, the more likely it is that a search engine might conclude you are a spammer.
Checking a partner site for spam potential isn't always easy. Experienced webmasters develop a "nose" for this, though - and periodically checking your partners is a good idea. You may not weed out all the bad ones, but even clearing out some obvious ones is worth doing.