As more and more things we might consider "platform" move to the cloud, I think it also matters what the service provider means by saying it's up. Just because the servers are alive and responding doesn't mean the platform is really functional.

One vendor in particular we deal with has a powerful feature which we use to a large extent. Unfortunately, that particular feature is all too often not working. The servers are up and the rest of the platform is working, but we need that feature, so if it's down, it doesn't help much that the rest of the platform is up.