- This is ridiculously common
- It's dismissed as an "antivirus software"/"user error" problem
Given that I'm not setting the knob, and it doesn't magically happen at restart (it seems to happen after I visit some pages), I think there's either an exploit (known or unknown) in AdBlock Plus, or some other functionality that allows pages to turn it off.
Given AdBlock Plus is a business, I wouldn't be surprised if they had such a thing, and were selling it to ad companies. Hell, knowing people in the ads business, and hearing their stories of the sleaziness of the ads industry, I'd be surprised if this wasn't going on.
I wish I could find the uBlock plugin for Firefox people are telling me exists, but searching is turning up nothing. I think it's just idiocy put out by "Chrome master race" users who don't actually have a clue.