Search engines like to take the hard line and categorize things as either black or white. In some cases, they are actually grey.
Say you are an artist and have a local frame shop you like to recommend. In turn, the frame shop might give you a small referral fee for sending all your wonderful clients their way. The online version of this is a link from the artistâ€™s website to the frame shopâ€™s website. It makes sense. Itâ€™s good marketing. Itâ€™s good business and that is what link-building and link buying is all about.
Many times, a link is a great lead generator. Letâ€™s take the artist and the frame shop example again. You might get tons of traffic from that artistâ€™s shop. It is a great business link.
You might buy links for credibility. Taken to the extreme, your link from the local Chamber of Commerce could be considered link buying.
Personally, I think link buying is a perfectly legitimate practice. I don’t see the difference between a banner ad and a text link ad, as long as you’re not intentionally trying to game the search engines and you expect to get traffic and brand visibility from those ads appearing on the websites you are advertising on, irrespective of the SEO effect.