There was a good article around called something like "the well that Google built"... (Ironically I can't find it on Google).

But the basic idea is like building a village well. The rich people of the village may band together and build a well - naturally, they don't make money off it, as the general populace would be too poor to pay.

What happens is that the prosperity of the whole village increases. Disease goes down, productivity goes up - so the demand for what the richer inhabitants have to offer (e.g. goods & services) goes up.

The Internet is all about this - Google isn't the only example, but is a prime one. Whilst many of their services do not directly make any money, they make the Internet a more useful, better place... And the more that people turn to the Internet, the better off Google is.

Edit: pg touches on this too, with his comment about a startup tackling an issue like malaria: http://www.paulgraham.com/good.html Curing malaria isn't going to immediately/directly make anyone any money - but it's possible the downstream effects could generate a lot of wealth.