Business models based on user information

I am in the process of figuring out what business plan would be most appropriate for my online service. Essentially, the questions I'm asking myself are:

1. Can internet companies survive on providing a service completely free and making money from the information they collect about their users?
2. If so, what information do they need, and how can they exploit it?

The examples I found where Facebook and Gmail. Facebook collects information about the social graph of their users which helps them deliver targeted advertising. Gmail collects information about the conversational content of their users to also deliver targeted advertising.

Are there other examples out there?

There are a wide range of examples.

• ifttt. They get to watch what people are interested in and collect a lot of stats data.
• Bit.ly have a huge amount of trending data and access to key people so they can point to the people who get followed.
• LinkedIn. Directly sell access to "mailing lists" and market targeted marketing to business easy.
• A lot of the games sitting on facebook use the social interactions to generate activity which people then pay to get to the next level, get the next thing in the game.
• buzzfeed are a specilist viral CMS, they sell the tooling to make your stuff go viral. Now being used by Coke, Nike and a few others.
• Any of the good recommendation engines.

There are potentially a lot of ways of monitizing socail interaction

• Pay direct for contacts.
• Havesting the data collected, if you remove the names/emails and keep it clean then this is very useful and companies will pay a lot for it.
• Targeted advertising.
• Spreading the word. If your site can spread the word to a targeted demographic through people recommeding
• Putting people in contact (like Stackexchange)