I think it should be argued here that what you are trying to sell also really matters. 37Signals sells business software. I don't think you can get away selling social network software or search engines to consumers.

Also, social network-type software requires a critical mass of users in order for them to be effective. If all of your friends weren't already on Twitter and Facebook, perhaps you wouldn't be either.

It's not as straightforward as selling your software from day one to make money.