My startup is still on page five of Google and our traffic is almost all word-of-mouth. So it is possible but it is not fun. Very easy to get bitter when you see the spam that floats above your stuff and hear people tell you that Google rewards quality content, or when users write you to complain that they cannot find you.<p>Anyway, I would not try it with multiple founders. It is hard enough to get yourself to the point of making enough money to pay rent/food for one person without strong distribution without having to worry about multiple partners.
The company I currently work for started with zero marketing in the mid 2000s (2004/2005). We grew into a multi-million dollar company. We're in the home and garden e-commerce category.<p>We didn't really start doing any marketing until 2010 (Google TV, at that!). Now, though, competition is a mess (tiny sites rank above established brands) so we're almost forced to do some form of PPC. In some ways now, you're completely at the mercy of Google and their latest algorithm update, regardless of whether or not you follow the SEO rules.<p>To answer your question though, if competition is low it can definitely be done, just do everything with SEO in mind, but design and write for users.
Yes, there's plenty of other options such as PR, virality, social media, SEO, etc. However in general if you're not paying for traffic (in addition to your organic traffic) you're probably leaving money on the table.
I grew clalerts.org from 0-800 users via organic methods in about 4 months.<p>Google "craigslist alerts" I have links coming from a ton of tgose results.<p>Fyi Craigslist shut me down 3months ago.