But I also think that Facebook is already on its way down, people seem to have moved on. At least according to their numbers they still seem to grow or at least remain stable but I would guess that this is mostly due to expansion into new markets and if people there go through a similar trajectory it is only a question of time until the last new market starts and eventually stops using Facebook.
Here in Germany MeinVZ [2] was the dominant social network until people started moving to Facebook and now MeinVZ is just a ghost town. And it pretty much feels the same with Facebook now, actually already for the last five or so years, people come back and engage more and more infrequently until they eventually disappear. It is much slower as compared to MeinVZ but I am pretty sure it is essentially the same thing.
I am not sure where they are all going, maybe Instagram for the younger generation, maybe just WhatsApp for friends in my age, so Facebook the company might just be fine for some more time even if Facebook the network dies. But things have certainly changed from this madness of, I don't know, somewhere between five and ten years ago, when Facebook became inevitable, when it was constantly in thew news, when every ad poster featured a Facebook link.
I would neither be surprised if it turned out that Facebook was an essentially quite short-lived onetime phenomenon and people were not that interested in a global community as the social media proponents would want you to believe, nor would I be surprised if every generation had its own Facebook even if just to set themselves apart from the older generation. Why would we even assume that social media is more than a fluke and does not die away just like many things before?
Only if enough of your friends were on it to make it worthwhile, the danger is that many of your contacts would disappear, which would lessen the value of facebook for even more people, leading to a vicious cycle. And even if it didn't happen to your social circle it would stem the inflow of young people even more than is already the case).
Then it's not much of a business, period.
In my ideal world, we'd only have businesses where the costs are open and direct (e.g. no "user is the product" or selling of personal data, or even "ad-based").
If they can't make it in this way, then, sorry, they don't have a business model.
Well, if there are no buyers, then why have a product?