Just noticed the sponsored ad links on Gmail are related to the content in your message. For example, an email from my friend included news about her guitar skills and yoga practice. The sponsored links included ads for guitars and yoga retreats. I felt a little violated by this discovery. It’s brilliant, of course. Relevancy wins on the web.
Actually, Google explains this nicely. They use the same technology as their AdSense Program to deliver relevant links based on content. All is good…I’m comfortable.