On social networking sites or ad listing sites like Twitter or Craigslist, how is the community built?

[Daniel]

Take for example Craigslist, it's huge now but initially why would anyone post anything, and how did those individuals see success if there was hardly anyone on there? If you were trying to sell a car, who on earth would have bought it? How did it grow?

[GFNGeek]

social sites like any site, grow because they are recomended or people see them as a good idea, you will find that things always start small, you see 1 or 2 people sign up, they like the site, they recomend it to their friends who check it out, and so on until there are lots of users, for sites that sell again they start small, you dont go on a new site and sell a car, you sell a CD, you sell a watch, and when that goes well you get recommended, so others sell a watch that goes well they sell a TV, that goes well you sell a bike, that goes well you sell a motorbyke, that goes well you sell a car a house a company, and if you have problems the site proves they can handle it and that gets passed around. and over the months you get bigger, more people start using you and recomending you and soon enough you have amillion users, but then the oposite is also true, you start small you make a mess of the selling process no one recomends you and you dissapear forever....