I wonder if there is a point where signal to noise in advertising gets so low that the industry itself collapses. Many people actively ignore advertisement at this point, but there is still enough attention to make paying for them profitable. I don't see any reason that couldn't change in a sufficiently noisy environment.

If demand for advertising drops too low as a whole, and ad supported content goes away as a result, is there enough of the internet left to maintain critical mass and keep existing?

Maybe spam really does win in the end.