The site is specially designed so that once someone submits an ad they can also login and submit an email advertisement.
The email advertisement will stay on the server, even if their ad has been rotated off the ad board.
When they refer people to your site with their special referrer link and as those people place ads,
the email advertisement of the person who referred them will be send to the person that they referred.
This works on 3 levels. For Example: Bob refers Mary, Mary refers Fred, Fred refers Jill - Jill would get an email from Bob, Mary and Fred automatically sent out from the site.
This is called viral advertising and it is a great way to get people to tell other people about your site.
So if each person just gets 10 people to place ads your site could be spread across the web very fast.|
We call this Viral Advertising because it can spread virally.