PLAYBOY: Portals attempt to create what they call sticky content to keep a user as long as possible.

[Google co-founder, Larry] PAGE: That's the problem. Most portals show their own content above content elsewhere on the web. We feel that's a conflict of interest, analogous to taking money for search results. Their search engine doesn't necessarily provide the best results; it provides the portal's results. Google conscientiously tries to stay away from that. We want to get you out of Google and to the right place as fast as possible. It's a very different model.

But that was in 2004. Things have changed.

via Google Is Facebook Is AOL: What Happens When a Good Google Goes Bad