I'm not sure I agree that #9 (BabyCalc / automated baby progress emails) would have been a flop in and of itself; it just sounds like he had a personal reason to fold the business.

BabyCenter.com right now is hugely popular among soon-to-be parents. What's one of the key things that gets parents to sign up in the first place -- almost immediately after they find out they're going to have a baby? Weekly emails detailing the pregnancy's latest progress.