I have been thinking about the ad bubble in particular, for which Google is not the only one responsible of course. Of course, it is all ultimately funded by debt. I wonder what Larry and Sergey will do when it ends.
The quintessential examples of this phenomenon are Twitter, and potentially snapchat.
The idea of the "ad bubble" is that you have to have a massive amount of users to make the system work. And if growth stops... Well there goes your company.
The bubble is that ads can't really pay for the ridiculous valuations that some of these companies are getting.
even google could suddenly become a lot less profitable very quickly. many of the 260~ unicorns spend a lot on ads, a revenue stream that could disappear quite suddenly.
i'm not saying its likely, just that it could reasonably happen