I'm thinking of adding a sponsorship option on my blog posts that allows people to buy ads on a post by post basis. For example, it would say "This article is sponsored by X" or something to that effect. I found one solution. It's not perfect, but it does allow me to do that and does have the option of making links nofollow. Would nofollow be absolutely necessary? Would it be SEO suicide to leave links as dofollow? I don't want to hurt search engine rankings, but I also know that if links aren't dofollow, it is unlikely that anyone would want to buy links on a post by post basis. Thoughts?