There is a fundamental problem with the way the web is working now. We're in a kind of limbo. Companies like Dropbox and Airbnb (and the company I mostly work with) actually sell a product and as you say they're good.

I've been having a hard time formulating what I'm about to write so I apologize if it doesn't make a lot of sense. I can't help feeling that the Facebooks and Twitters are using the web in a way that there really isn't a proper infrastructure for. They seem to be quite expensive to maintain and, by nature don't generate lots of money by what they do. In my opinion, if they charged they wouldn't be able to build the big networks of interconnected users that defines their value.

I think there are ways past this conundrum but I don't think that profit motive will be the what pushes them and I think they will require a somewhat different infrastructure than we have now.