JS_Harris - 5:24 am on Feb 28, 2010 (gmt 0)
When link buying became the rage several years ago, before Google really tried to crack down on them, I tested the waters by selling 10 mid-article links on a non-important blog I was writing.
To my surprise they immediately sold out, 3 of them to one of the major SEO companies in business today, and those pages didn't last very long in the serps.
I think links within context are the most valuable and that they must be there from the day the article is first discovered. Adding links in the middle of articles later on isn't natural and may trigger red flags too.
In the end I removed the paid links and have not bought or sold a link since, there really is no need to if you take care of everything else imo. I sleep better at night too.