It seems plausible that the network effect that's responsible for Facebook's current success could also cause it's rapid collapse, as knowledge of a viable alternative to Facebook could easily propagate via Facebook itself.
The success of a viable alternative need not be generated instantaneously as a result of some egregious action or catastrophic failure of Facebook. It can slowly grow by accretion as people who are unhappy with Facebook's persistent flaws seek alternatives, and once that population is large enough, then it will become a critical mass and start drawing others in.
Facebook itself grew via a strategy of becoming dominant in increasingly large concentric circles around its initial core - first Harvard, then Ivy League universities, then universities in general, then organizations in general, etc. With each iteration, they used their dominance within each narrower sphere to attract new users from the broader sphere, by relying on the broader population's desire to be where the "cool" people are. The implication here is that if the "cool" people end up leaving Facebook - even if only in search of novelty - then some other alternative will have the ability to build up its own userbase in the exact same way that Facebook did, and in exactly the same way that Facebook undermined MySpace.
The success of a viable alternative need not be generated instantaneously as a result of some egregious action or catastrophic failure of Facebook. It can slowly grow by accretion as people who are unhappy with Facebook's persistent flaws seek alternatives, and once that population is large enough, then it will become a critical mass and start drawing others in.
Facebook itself grew via a strategy of becoming dominant in increasingly large concentric circles around its initial core - first Harvard, then Ivy League universities, then universities in general, then organizations in general, etc. With each iteration, they used their dominance within each narrower sphere to attract new users from the broader sphere, by relying on the broader population's desire to be where the "cool" people are. The implication here is that if the "cool" people end up leaving Facebook - even if only in search of novelty - then some other alternative will have the ability to build up its own userbase in the exact same way that Facebook did, and in exactly the same way that Facebook undermined MySpace.