So, a server rental model. Good money, but not unlimited. If you want to go big, ads is the only proven model at the moment. 

The three main business models (and incentive schemes) are:
- ads (make users buy as much as possible)
- rev share (make users zap as much as possible)
- server rental (make users use the attached services as much as possible). 

Ads is by far the largest compared to the other two.

Everything else is small business.