The "build it, they will come" strategy. It has never worked as a strategy for marketing, ever, in the history of ever. Viral marketing, the "network effect", call it what you like, is only successful if it's backed by a pretty huge advertising budget. Not necessarily traditional advertising, but behind pretty much every successful "viral" campaign that's selling something there's an agency who are pushing the right buttons to get things shared.

If you don't have the budget for that, you have to put in the legwork in traditional marketing and selling. It's a horrible, hateful reality of startup life - the fun coding stuff actually comes a distant second to being a salesperson, especially at the beginning before you can afford to pay someone else to do that stuff.