Truthfully, I've never run an ad blocker before, until over the summer I got extremely fed up with a particular web site that I keep going to out of old habit (slashdot.org). A couple times I left a browser tab on the site, and in the middle of the night some video ads started playing through the computer speakers. And over the summer, I was at the camper on a hotspot connection, and accidentally burned through my entire month's bandwidth allotment because accidentally left their front page open when I went hiking for a few hours. Again, those aggressive video ads.

So I installed an ad blocker, which actually made my 3g wifi hotspot usable over the summer. (Yes, I should stop visiting sites that get too annoying with aggressive ads, or I should just selectively block those sites).