Maybe we should re-aling the forum to the question: What sort of links can you buy that will be beneficial for your rankings and not harm you?
I sell advertising from my websites, most commonly in the form of advertorials (a small banner with a textlink). Most customers buy them for the sake of direct conversions, some realise that there is a real value for SEO, too. In addition, I have three to five external links from every article on my site; plus, I limit advertising customers to locally and thematically relevant ones (eg. in my area and industry). I think it is very hard for google to recognise these links as being "paid" - and even if, so what? I link to sites that offer products that might be of use to my readers. Isn't that what advertising is about? The border between "paid links" and "conventional advertising" is blurry!