I think you've overlooked something: people can leave a social media site without deactivating their account. I haven't used Digg or Slashdot in at least a deca

I think you've overlooked something: people can leave a social media site without deactivating their account. I haven't used Digg or Slashdot in at least a decade, for example, but never got rid of my accounts. I've also got a few alt Reddit accounts that I haven't logged into in a long time. I'd expect in general the number of people who leave a site but don't bother to actually go through the steps of deactivating the account to be quite a bit higher than the number that do deactivate.