Facebook's promoted posts seem like they would be controversial, they're a way for people to pay to have their regular posts shown to more people than they normally would.
But Facebook gets to choose how many people see any of your posts, so it's essentially asking you to pay so it won't bury your post.
People make a much bigger fuss about things like facial recognition, which doesn't really affect anyone.
Facebook users, that is to say, people – since at one billion users, they're a very representative sample of the human race, are peculiar like that.
It's a good thing Facebook doesn't listen to them all that much and rather relies on actual facts, that you can quantify.
Like the fact that 2.5 million promoted posts have been paid for by small businesses, or rather Facebook Page owners in general.
Two percent of existing pages have used the product, some 300,000 so far. It's not a huge number, but it shows there is interest and potential.