It is the eyeball bubble. The quintessential examples of this phenomenon are Twitter, and potentially snapchat. The idea of the "ad bubble" is that you have t

It is the eyeball bubble. 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.