I've got zero problem with it if its from some webmasters flying under the radar and don't do it as a biz model

What's the use of it? You can generally get way more out of the money rou are going to pay for a high PR link.

I don't think link buying is a very good idea.
Since google looks for quality links when ranking, there might be a risk of the links not being genuine.

I think link buying is an expensive way of SEO and also an easy way for gaining backlinks. I would suggest for quality link building process this is more likely by google.

Google sells links...they just call it Adwords. Those are the only kind of links I have ever purchased.