> But it seems like very few large advertisers would move some budget off Facebook if potential reach was 10% lower. Very few advertiser’s budgets are constrained by audience size.
Why wouldn't an advertiser invest less in a campaign if it reached less people? That's why companies are willing to pay so much more for a superbowl ad than a regular TV ad, because they have more reach.
The problem I think is that a lot of advertisers, especially smaller ones, wouldn't want to risk pissing Facebook off with a lawsuit. Plus even if Facebook misleads advertisers in a way that results in them spending more money than they otherwise would...the fact is, Facebook could likely double or triple their current prices and those same advertisers would still pay it because they have no choice.