if they don't sell products or services, i guess they make money from advertising. for example i see dell advertisement on the top of this website, this mean dell paid some money to advertise here. and by saying that a website can sell smth i don't mean like t-shirts or stuff. fore example if answer bank wanted to make more money they could allow to post 2 questions a day and then ask you to pay by sms for posting a third question. i'm not offering this kind of system :) it's just an example :)