But doesn't that just seem unsustainable and like a recipe for disaster? In the example you mention Reddit the company is basically tieing it's entire existence to Google's adtech. If google suddenly decides it wants to come out with a competitor and shuts down Reddit's access to the adnetwork, the games over for them as a company. They have no ability to build 1-1 relationships with advertisers because they aren't one of the big players?

This also seems like something ripe for abuse. You use Google's AdNetwork because it's the only way to access revenue for advertisements. But google can keep upping the cost of it and companies are left with no choice but to pay it or fold up shop.

Maybe this is a good thing and companies shouldn't be relying on ad revenue. This is basically what I tell everyone who comes to me with a startup, mobile app idea. But at the same time, there are companies that provide real value that don't have a lot of other good avenues for revenue.