Google employee Jon Rockway made this point, which I thought was interesting:
Up to a few years ago, Google used to use Yell to supply local content. Now, it’s overtaken by Google Local. For years Google has been taking money from credit card companies and comparison sites alike. Now, it has launched its own version, which it uses Adwords to push.
SEO isn't an area I have much experience in, personally. What are everyone's thoughts on this?