Accd to an ex-Googler, yes. “In a new book, “Subprime Attention Crisis,” former Google executive Tim Hwang contends that since behavioral targeting doesn’t work very well (and generates lots of hidden costs), digital advertising is a bubble that could burst as soon as marketers figure out their ROI is terrible.”
This could be legit; there are certainly fads (paid, earned and owned, anyone?) and wild performance claims with dubious or nonexistent evidence (native, lots of programmatic) but a bubble of the scale of the subprime mortgage debacle that will bring down the largest publishers? Ehhhh, unlikely.