How do they market a new website?

[O]

Such as facebook, YouTube, Twitter, ebay, ect...

If you have a new website such as those above you don't have any data base of people so imagine facebook just lunched its website, you enter the site and you will find a couple of persons (most probably the engineers and their families there.

I guess you will not add your Profile right.

How come now these sites have thousands of members.

What is the marketing strategy.

[marke22]

The same as other popular things...

Press releases sent out to internet publishers, newspaper publishers, talk shows, radio stations and magazines.

[Jakester]

Those were all press worthy innovations which received free publicity through news reports.

Site flippers building up more conventional forum sites habe been known to employ shady tactics like paid participants and scrapped content from other forums to 'seed' their site with activity, resulting in quickly inflated ranking and resale value.

(It's tough getting a forum off the ground, no one wants to be the first member)