i would say a link is a link.. I was starting to think spam was bad.. now i'm starting to re think that..
Links are links, take one whenever you can get one. If bad links do harm to a websites rankings you can just start getting bad links for all of your competitors. Pick up links whenever they are available to you, they will do you good in the long run.
i dont the question is whether there are better things to spend time on, but whether it is worth doing at all. One of my competitors does tons of spammy links and they are doing a-ok with the search engines.