I am just trying to provide alternatives. I have no idea what twitters revenues are. Perhaps a tiered system like mailchimp has? If you have under a certain amount of requests it would be free. Paid applications which heavily use the API could be charged more.

Also, as I mentioned in my comment above, I think a premium subscription would be in order. I would pay for a service that saves tweets, and provided basic analytics. I am just trying to get the conversation going about alternatives. If anyone else has possible revenue alternatives for Twitter, I'd be interested to hear them.