Maybe. A lot of people have been saying this for over 10 years. If it's a bubble that's real though, the effects are going to be pretty widespread. Not only do two of the biggest (and best-paying) tech employers get slammed, but so do all the inter-related companies. And, also BTW there will also be a lot fewer fat exits for startups if Google and Facebook acquisitions get turned off.
First sign to me that the dot bomb was imminent was a two inch article in the WSJ summarizing a finding that something like 2/3rds of startups had board members or upper managers that had been sanctioned or investigated previously for securities fraud.
It's telling that all the FAANG companies are basically in open violation of a number of laws.
