If Facebook transitions to its new hardware and the hardware begins to crash and burn and users start getting affected, so will Facebook... there are competitors who would love to have Facebook's lunch. So reliability is pretty up-there for Facebook too.
If Facebook is down for 2 hours, you're not suddenly going to sign up on MySpace. By contrast, other companies can lose millions of dollars in that same timespan!
Major stock exchanges have gone down for hours, I've had trouble reaching my bank's web site for hours. Let this myth of the enterprise having any idea of what its doing die.
And Facebook could lose millions of dollars in that time span, depending on what time of the day the downtime occurs. They make money from advertising, down-time means no clicking and no eyeballs.
Facebook regularly pisses off large swathes of its users and they stay anyways. You can look at basically any feature they launch and subsequently have users trying to revolt over or the numerous privacy scandals.
