That's because we are really good at hiding them. No, there aren't any ads. We don't bring in any revenue right now, in fact we don't even make money on the swag. We created Hubski to be a thoughtful place to create, share and discuss interesting ideas etc. It certainly wasn't for the $. That said, our server costs are going up and we may end up needing more help to keep the lights on, so we will be implementing a donation mechanism in the coming weeks. At least that is the plan.
mk posted some thoughts on the aggregator as a business model that gets to why we haven't taken any funding etc.
Edit: In short, we always describe Hubski as a project and NOT as a startup. We don't like the connotations associated.