The corollary of Metcalfe’s Law is that every time you subtract a member from a network, its value drops in half, along with the number of possible connections. When you #DeleteFacebook, you make it easier for the people in your friend group to do so as well, because you are no longer part of the reason to continue using the service.
It can become a fast-moving syndrome that can literally decimate the user base in the space of a few months, as we saw with MySpace and the walled-garden on-line systems that preceded the Web and popular use of Internet.
Here’s hoping that happens with FB. I wish there more instances of federated services like Diaspora and Mastadon that replicate one-stop-shop social network functionality out there so that there was more adoption by people leaving toxic services like FB and Twitter. However, there are plenty of existing and widely used services (e-mail, SMS, RSS, photo-sharing sites, event/invitation sites) that can be used an alternatives to various pieces of FB functionality with a little education.