Add the ability to flag domains as spam, this could be community driven for example "500 users flagged this as spam". Then give the ability filter out spam from link profiles.
Tbh, I don't think this is a good idea simply because the majority of people "being able to vote" are simply incompetent, misinformed and more often than not, not being capable to understand core concepts simply because being narrow-sighted. Just look where democracy got us to. :o)
@Karamarinov: Interesting POV, thanks for the feedback. I still think a moderated spam list would provide an additional layer of insight on metrics such as DR and UR, but to your point, should be considered an advisory metric only.