The members of our group all work day jobs doing medical informatics, so we're more or less medical data geeks who identified a hole in the medical informatics field and exploited it. I do it for it fun, although I can't speak for the other guys in the group. I'm the main programmer so I get a certain amount of enjoyment watching our traffic grow. Even though we're not monetizing our traffic (ads, etc.), there is a sense of satisfaction we get knowing we're empowering consumers, providing a research tool for pharma companies, providing actionable data to physicians, and generally taking obscure messy data and making it clean and usable. This project is very satisfying. Right now we're just happy knowing other people find it useful.