Over at WebHostingTalk, a very popular forum in the web hosting industry, there's a thread about buying links vs. earning them. The advice tends towards a very white hat point of view, but one member in particular, the_pm, sums it up so eloquently that I couldn't put it better myself:

IMNSHO, paying for pagerank v. seeking out legitimate links is the difference between meeting someone, falling in love and getting married v. paying for a hooker.

Since it's a rare Saturday night post, I figure even SEOmoz is entitled to have a little risque content...

BTW - Special thanks to Geraldine for the suggestion of what to use as an image for this post. Yahoo! image searches for related terms were bringing up some very inappropriate content.