[jasode]

>If everybody used a DNS blocker to filter out ads, would online advertising exist as a business?

Absolutely. Companies would get more clever about cloaking advertising with inscrutable domain names that's hard to filter with regex. Youtube is a good example of ads that are hard to block using pure DNS. (But that doesn't stop people from trying new variations of regexes for pihole that youtube eventually breaks.[0])

The other technique is native advertising. (But native ads are actually more "relevant" so somewhat more tolerable and more people would actually pay attention to them.) E.g. I just saw a Linus Tech Tips (the computer tech channel) and the pre-roll ad is for D-CON mouse traps (not relevant to me since I don't have a mouse infestation that requires rodent traps) or girls dolls[1] -- but the native ad is Linus acting as spokesperson for the Ring Doorbell Camera Kit[2]. That's more relevant since it's a techie gadget. I won't buy the Ring kit but it's more relevant than the mouse trap ad.

[0] last time I tried many of these DNS regex ideas, youtube stopped working: https://www.google.com/search?q=pihole+regex+block+youtube+a...

[1] ads for girls dolls probably ignored by 99% of audience demographic of Linus' video: https://imgur.com/a/gPcxOJ3

[2] https://youtu.be/hiLlNzxDfAg?t=19m12s