This makes complete sense to me. I’ll explain with an analogy.
When you first got high-speed internet at home, you likely spent the first week downloading every MP3, video game, or movie you ever wanted. Eventually, the marginal utility of downloading an incremental bit of data fell, to the point that your actual data usage probably wasn’t much greater then what it was when you only had a dial-up connection. In that sense, your “engagement” dropped.
Facebook is suffering from the same thing – although “suffering” hardly seems appropriate for a company with a 9-figure valuation. Early on, it was interesting to see new, embarrassing photos of your “friends,” but a few years in, you just don’t care anymore. So you still check Facebook, but you spend less time on the site. Or, as in the case with these numbers, you don’t even log in at all.
There’s a second effect that is being felt.
Normally, things like Facebook are driven first by early adopters, and then by engaged contributors who upload quality content regularly. This is an extreme manifestation of the 80/20 rule, where 80% of your interesting content is added to the experience by 20% of your users. Except that on these sites the ratio is more like 95%/5%. And given how mainstream Facebook now is, I’d be willing to bet that the ratio is even more skewed (99% / 1%?), since most “mainstream” users share nothing more than photos and the odd status update.
The problem is that, with every release, facebook is going out of it’s way to piss of the 1% of users who contribute.
Facebook depends almost entirely on
user generated social content. If you piss off the 1% of users who create the valuable content, then the experience of the entire user base goes to shit. Yes, you still have to go there because all your friends are there, and because you need to collect your Facebook messages, but you sure as hell don’t spend any more time on the site than you absolutely have to.