Google. That's the one everyone points to.

There're a bunch of other ones that look like they're not making any money, but actually are, usually through advertising or corporate deals. Reddit. FaceBook. HotOrNot. PlentyOfFish. LiveJournal. MySpace. Skype. YouTube (though I believe YouTubes revenues are less than Google expected when they bought it).

Generating revenue and making money are generally considered two different things in business circles. Many believe that making money implies being profitable. It can have the meaning you are ascribing to it. That is, having customers give you money, that's generally considered to be only a part of making money though. The other part is keeping costs low enough that your business generates a profit. Even subject to the more stringent requirements, several of the companies you mentioned qualify.

I have doubts about YouTube being profitable, perhaps you have some inside info on this though. Certainly Google's quarterly reports indicate some challenges there.

Similarly Facebook could be massively profitable if they would cut costs. That profitability would fall well short of justifying a USD15 Billion valuation, but they could be more profitable. It is difficult to tell whether or not Facebook is profitable at the minute, because they can give any story they want as they have yet to go public. Whoever said 'There are lies . . . damn lies . . . and statistics', was probably unfamiliar with the world of corporate accounting, or they would have used 'accounting' in place of 'statistics'.

if you have any intent of getting money out of a startup or running a successful business, you need to design and build with the revenue model in mind. even if its a purely ad-driven model.

companies have fund success building first and monetizing later, but its the exception, not the rule.