It seems to me these companies are pretty much just re-slicing the same sized pie. No real growth in the aggregate. Long term these exorbitant PE's need to contract.
https://www.bloomberg.com/news/articles/2014-03-03/advertisings-century-of-flat-line-growth That means the only way to expand in this business is to steal share. “Everything is a share game,” says Goldstein, as declines in older media give way to growth in newer media. It has been a continuous trend from the beginning. New media do not increase ad spending–introduction of radio, TV, and the Internet has never, in each case, caused the ad industry to grow faster than the economy; they just shifted how the existing dollars were split. More specifically, you can see Internet spending—the latest “new medium”—is now at a 20 percent share. That’s about the same as where radio spending was prior to the TV years.
Cannibalism within FANG? What's Cramer going to do now? I believe $GOOGL will hold up, they're a bit more diversified than $AMZN and $FB.