MySpace didn't suddenly disappear, it fizzled out over a long time. Also, the relevant metric isn't the total number of users -- this is a massive parallellisable process -- it's the average network-effect lock-in per user. For one thing, networks are fairly segmented around geographies. And that's what makes the MySpace analogy relevant: people thought it would never go away because it had very strong network effects, everybody you care about is on it.
Facebooks demise doesn't require the coordinated action of two billion people. Network effects work the other way as well: when people do leave, they make the experience a little worse for all their contacts, lowering the bar for them to leave as well.
Sure, the number of users probably extends the long tail of the demise, indeed I expect Facebook to hang around as at least a low-engagement contact book/messenger platform for a long time. Their demise will look more like Yahoo than MySpace, but the MySpace story does tell us that network effects aren't magical spells that can never be broken, and network effects are Facebooks most important moat.
Facebooks demise doesn't require the coordinated action of two billion people. Network effects work the other way as well: when people do leave, they make the experience a little worse for all their contacts, lowering the bar for them to leave as well.
Sure, the number of users probably extends the long tail of the demise, indeed I expect Facebook to hang around as at least a low-engagement contact book/messenger platform for a long time. Their demise will look more like Yahoo than MySpace, but the MySpace story does tell us that network effects aren't magical spells that can never be broken, and network effects are Facebooks most important moat.