It doesn't work, not for me anyway.
my campaign was monied out by a site I wasn't getting a ROI from. I can't do anything about that save for pulling the campaign. I pulled the campaign rather than waste my money every day. Had i been able to remove the offending site I may well have found sites that would give me a ROI.
It isn't true to say that everybody has the same level of control. Publishers can block ads they don't make enough money from. Advertisers cannot. Hardly a level playing field.