Basically, since there are no search engine advertising opportunities available, people in this business are almost forced to resort to these sort of things, especially when you see the people that use this tactic being rewarded in Google. There really isn’t that much risk as I’ve read where other sites have been reported before and the search engine does nothing for months, if ever. That’s enough time to build a nice player base.
Where I see it hurting someone is a situation I ran into recently. I inquired about advertising at a blog and was told that if my site had ever spammed their group of blogs in the past they would not accept advertising from me. So yes, it could hurt you down the road. And I would also be worried that eventually the search engines are going to stop counting these as legit back links.