wheel - 10:53 am on Apr 14, 2010 (gmt 0)
It's not about Google's guidelines. It's about Google's lack of any type of enforcement of those guidelines, now ongoing for years.
It's not just about directories. It's about huge amounts of directories. It's about themes sponsorship. Huge blog buys. networks.
The risk is you get penalized. It used to be every time there was a Google update huge swaths of sites got penalized. But when everyone's doing it and hardly anyone is getting penalized then it's no longer much of a risk.
Folks suggest that sites with unpaid links should be your main strategy, and tinker on the paid links. I wonder if that's not backwards. Keep a site with unpaid links as your backup, and work on lots of paid links to your main site. That's starting to seem like a smarter way to go.