[NeoVeles]

There is the book on this called 'Subprime Attention Crisis' by Tim Hwang that tries to argue this point.

It is only partially successful in its goals of saying the sky is falling.

The overall message I came away with was that online advertising has some serious issues that need addressing - but they aren't anything that cannot be solved.

If there is a bubble then I suspect it isn't anywhere near as big as it is made out to be and that any "crash" will be more of a slow correction than the bottom suddenly dropping out.