How do companies like friends reunited/you tube/stickam make money from us ?

advertising in most cases

Youtube hasn't actually made any money yet, Google bought it because it could make money in future. In theory companies could pay it to put their videos on top of searches.

I haven't used frends reunited in a while but I think you have to pay for a subscription to use certain services such as actually contacting people.

Most sites rely on advertising of some sort or an upgrade to a full subscription service

In you tubes case I would assume they have merchandising and such. Although I have seen advertising on you tube on almost every page. Not a lot. But when you are a huuuuuge site like that,.. you can charge major cash for little advertising. And when you got other big companies paying you millions for your site.. who needs to make any more?

Friends Reunited makes money by charging subscription fees. Youtube doesn't make money (yet - Google will integrate Adsense soon enough). No idea what Stackam is.

Advertising dollars. Companies pay to have their ADs on the website, like in newspapers that are free. The ADs pay for the site.

I paid £5.00 per year.With 6 million members thats a good wack!

you have to pay to use certain tools on the sites like emailing people and that