While this is true for the largest of ad companies like Google and FB, the same isn't true for the vast majority of recent tech IPOs like Robinhood, Duolingo, Couchbase, Monday not to mention literally all of the ridesharing and food delivery companies to name just a few.

In a way, excessive acquisition valuations are likely also a side-effect of too much money floating around that might change radically with increasing interest rates.

So then the question becomes what's the profit margins? Can they absorb, say, a halving of revenue short term?

If they can't then they're going to start layoffs, and the first to go will be the ones that don't generate revenue, so the experience gets worse for users, and the pipeline of new products dwindles, and you've released a bunch of potential competitors that know your business into the labour pool.

This also removes the price support for those existing startups.

In a time of genuine hardship, particularly of the energy/food constraint kind, there are a million consumer priorities before a new iphone (Apple), consumer electronics (Amazon), fast fashion, vacation travel, and the enormous adtech ecosystem (Google, Facebook) that is supported by such business, as well as the toolmakers (Adobe) for them.