Posterous appears to have a very large market for its product. Of course, its practice of releasing often, working hard, and communicating well has helped Post

Posterous appears to have a very large market for its product. Of course, its practice of releasing often, working hard, and communicating well has helped Posterous find a good product-market fit. But it's worth bearing in mind that lots of companies do 1-3 and still fail---typically because the market just isn't there.