I hypothesise user engagement would suffer in the face of down time. This, plus the added scrutiny this technical failure would place on their stock, means now is not a time when they can be careless about reliability.
I disagree. There is so many social websites out there that you need your users to think you are the only option, If your service is down, people will have a look at others', and might them interesting.
No-one cares if vital utility x is working. It's not like they are texting their friends, about x being 'up'.
But if you take away x, often it highlights just how important it was, and it becomes relevant to them.
It reminds them just how much x, means to them.
Then, if x reacts to the adversity in a crowd pleasing way... instant karma and mindshare.
cf. new coke as well.
(speaking from experience in the hosting industry)