NoFollow was hailed as the saviour of our sites, the answer to comment spam, forum spam and poorly maintained sites.
The idea was that by adding the “rel” attribute to a link the search engines would know that the link isn’t endorsed by the site.
The syntax isn’t difficult and easy enough for a spammer to find, and walk away from.
Sadly, the spammers haven’t caught on, and continue to employ unfortunates to do their dirty work, hoping that one day someone will see the light and spend some money on their ridiculous sites.
A spam filled site is a neglected site, one where the owner has had good intentions but not the time or inclination to follow through. The spam becomes a red flag to Joe Average that the site isn’t maintained and to look further for the information sought. That the site will eventually be downgraded in the search engines is appropriate – it is after all, stale and abandoned.