You need to factor in time. As an example Microsoft isn't treated the same way it was years ago and IBM isn't the same as before Microsoft. I'm not suggesting

You need to factor in time. As an example Microsoft isn't treated the same way it was years ago and IBM isn't the same as before Microsoft. I'm not suggesting FB will become obsolete but people will use other services if they see value elsewhere. If that weren't the case then WhatsApp/Instagram wouldn't have grown so fast. Network-effects does not mean something is immune from disruption.