No. If they cared above reliability above all else, they'd be more likely to use something like HP's nonstop systems, which are from their Compaq purchase, where were from Tandem. You can hotswap the motherboards of those things with 0 downtime.
They run the backend of much of the airline industry (former delta employee).
Edit:
Links with more information for those not aware of these behemoths:
They run the backend of much of the airline industry (former delta employee).
Edit:
Links with more information for those not aware of these behemoths:
http://en.wikipedia.org/wiki/NonStop
http://h17007.www1.hp.com/us/en/enterprise/servers/integrity...