He proposed the following:
Providing a valuable service for free can attract a large and loyal audience. This is one case where the first-mover advantage is tremendous. You want to post your ads where lots of people will see them, which makes it hard for a new site to gain traction.
Design is secondary to functionality, at least for sites that are delivering a simple utility, rather than entertainment. When compared to a newspaper’s classified ad section, craigslist isn’t especially ugly.
User-generated content can form virtually the entire content of a very large site, if you choose your domain carefully.
With user-generated content and little effort expended on design and new features, it is possible to have a lot of traffic with a very small staff.