Ask HN: What's the Posterous business model?

I like Posterous, but I'm really confused about the business model. After I blog into it for two years, are they going to start charging me money? The fact that they were (are?) trying to monetize affiliate-able links sounds kind of desperate.

I don't actually raise this question to bash Posterous, but I was curious about it because I have an idea for something that is like Posterous but for a specific vertical. Well, it's not exactly like Posterous, it's just that I would have a huge head start if I had Posterous's functionality out of the gate. So I'm kind of standing here looking at this large hill of development effort and thinking -- is it worth it? Is my idea good enough? Are the lack of players in the space I'm thinking about an opportunity or a "no gas for the next 500 miles" kind of sign? If Posterous is free, can I charge for what is probably going to be something "less than" Posterous for a long while?