( I am not blaming slicehost but does "power outage" make any sense? Aren't there power backups? (and presumably an alert system for when primary power goes down?) If anyone has worked in/runs a hosting service, please enlighten me).
I think I'd rather not have 100% uptime and have periodically tested systems, to increase reliability as long as I know when my server MAY go down.
Considering how data centres are set up there isn't much they could have done to stop it :)
Looks like human error (during the servicing)
Personally I would just say fire the support people and use the money to hire somebody that can actually deal with servers.
Im not a rackspace user :)
But yeh; someone is probably getting a tongue lashing. Human error is so easy; even for experienced engineers and especially with live electrical equipment... (been there, done that, got the scars)