app.net tried, but it was not successful.
I'm fairly confident that Snapchat could make money charging their users, if the fee is sufficiently small. Say $10 per year, perhaps as an in-app purchase, with the first 6 month being free.
We also may have to accept that some of these companies, Twitter seems the most obvious, isn't actually providing anything of tangible value to the average user and therefore can't exist. Of cause if some investors wants to keep throwing money at Twitter to keep the lights on, they're more than welcome. I know I'm not exactly being friendly towards Twitter, but it's a great example of a company that needs to fail. The only reason they don't is because investors have already wasted so much money that they're desperately trying so save it in hope of making the money back, by some miracle. Part of it might also be that investors, journalists and bankers are so heavy users of Twitter that they fail to see that the business isn't sustainable.
In the end the user will always be the one to pay the bill. Either by directly paying, or indirectly via advertising.
(Even on this angle, the problem right now is that Facebook's ad algorithm is a bit, er, dumb. At least, it hasn't figured out that I'm far more interested in local business X, Y, and Z that I'm following and not whatever unrelated spam some megagiantcorp is pushing...)
I firmly believe product placement, and the information exchange that surrounds it, is _the_ monetization scheme. Unfortunately, not only Facebook's ad algorithm is broken, but pretty much everyone else's. They have come a long way nonetheless, ad targeting today is one order of magnitude better that it was only a few years back.
People want advice not advertisements. When someone has money to spend and a need to fulfill, to have the right "advisor" is an incredibly valuable asset. Imagine a bot that knows my tastes, my assets and basically my life. This advanced bot could psyche me, at the right time, into making valuable and exciting purchases. A bot I could trust would succeed turning my money into happiness. That's the direction current algorithms have taken, with ever-increasing (and rather suspicious) omnipresence in our lives, grabbing any input they can get their hands on. The key difference is that companies look after their interests instead of mine.
The problem really is that no one wants to pay for services, or no one is willing to try charging for their services. Ads are the "safe" option, but it will also make your users leave in the long run.
I was pretty baffled when a publisher wrote that they would rather make money from ads on their site, than make money from people buying a subscription. Service like Twitter, Snapchat and what not seems to be the same way, there's no desire to try anything but ads.
It is still my belief that at some point some large seller of physical goods will announce that they're pull their online ads due to lack of profitability. After that the entire online media business will be forced to charge their users, and we'll all be better off. Maybe it's just wishful thinking.