Facebook is an ad platform on top of a social media network. It's correct to measure those OAuth users as active, because they're still being followed around th

Facebook is an ad platform on top of a social media network. It's correct to measure those OAuth users as active, because they're still being followed around the web (any site that uses the FB platform, which practically is most), they're still part of the monetization platform, they can be targeted in ads, etc. That's what's really relevant to their business, not how many people post content on their FB wall or send messages.