I think internet advertising is massively overvalued, the initial bubble happened when the click fraud detection tools were nonexistent, and because Google hasn't been changed, everyone assumes their valuation is right and correct.
internet advertising as a means to sell garbage is overvalued, but it enables a system of pervasive surveillance that allows governments and companies to exploit your data offline too. As long as the tracking continued, the buying and selling of the most intimate details of your life would still be a massive and growing industry even if no one ever put an ad on a webpage again. Advertising is also effective at manipulating public perception/opinion though so it's not going anywhere either way.
I think internet advertising is massively overvalued, the initial bubble happened when the click fraud detection tools were nonexistent, and because Google hasn't been changed, everyone assumes their valuation is right and correct.