One question that always comes up with me.. why the heck would someone pay for Google AdWords, Google AdSense or any other Google service ?
First of all, no one clicks them.. Everytime you put a search on Google.. who would take a look on the sponsored links ? Everyone knows clicking such a link would get you to some nasty russian dating site.
Secondly.. why would anyone advertise in text-based advertisements. Yahoo there instead delivers a service with beautiful banners and even flash animations.
The reason is that people are too stupid to think straight and only follow what others do.