Hi bb1webs,
Sorry mate, I got sidetracked by another comment that was made and misunderstood the issue; Its not the other site linking to you its you linking to a site that was penalised for blog spam.
Its still a simple answer; add a nofollow tag. Your friend will still have a link, just not the PR bleed.
WOT is Web of Trust and its a firefox plugin that lets you see the reviews of others regarding security, spam content, malicious software and so on. It has a way to go but its a quick way to see if anyone on the web has ranked a site dangerous, and I think based on where search is going, may be a great ranking tool if not a quick head’s-up on a site you are going to link to or from.
Sorry for the misunderstanding.