Earlier quoted context omitted.
I swear this type of comment is becoming like a meme, it's pretty much repeated on every HN thread about Firefox. The response is standard too... Electrolysis. Wait for it. https://wiki.mozilla.org/Electrolysis/Roadmap
I'm kind of hoping that Eloctrolysis never becomes main-line. Right now I have a browser that isolates misbehaving web pages (Chrome) and a browser that allows me to have a million open tabs simultaneously (Firefox). If I could only choose one I'd choose the browser that isolates misbehaving web pages but both is even better.
Originally the idea was for every page to be isolated but that didn't scale so well.