Ads ..Difference between Google and others

I was reading a few posts and couple of thoughts crossed my mind.

- Google has been extremely successful with AdWords and their Ad model. They can pay for the users as well.

- The other guys like Twitter, Facebook or any other social networking platform has not been all that successful though the level of relation with the end user is much higher.

The difference is that Google is a intermediary while others are just a platform.. This helps Google to charge fees and also to provide some back to the users. If we are able to break away from this difference, I feel there may be a new business model that may emerge for the social networking space.