More "did" than can. Something is worth what someone will pay. Why was FB willing to pay $19B? The answer is somewhere between what those users are worth to FB and the threat to FB's (very real) business that WhatsApp represented. This doesn't seem bubblish to me.
My understanding is that social networks are a generational thing. Even if FB was perfect in every way, no market maven teenager (for social networks the market mavens are teenagers) wants to hang out with their aunt. The next generation will stop watching Yo Gabba Gabba, grab their iPhone 9's and want to get on a social network that's separate from their parents. Because of this, I don't see a general purpose social network surviving for longer than 10-12 years and maintaining market dominance.
FB won't be the powerhouse that it is today, but it's deeply entrenched in our internet that there is value in the social data, not the "blue room" product they offer for free now. (I hate FB, but I get it.)
Mind you, it seems like a really low quality user for FB and not something I would want to hang a bubbilicious valuation on for them -- unless FB's able to track her activity off FB as well. And I think this is the case.
I wonder if this is part of the reasoning for their increasing centralization by offering a browser and supposedly actually hosting highly shared content.
I've never been to keen on that statement. It approximates something about fairness. It's expresses something about subjective worth. But, we're talking about something with a fairly objective, if ambiguous value.
The price of something may be what someone will pay. For the value of something... I don't think this holds true. The value of a stock is objective, it's the future incomes discounted or somesuch. If you pay more than that you over payed.