mm I would guess the odds of your local software being unavailable for a short amount are greater (power cut, local file server issues etc). Or if that's not true, at least the chance of catastrophic failure is probably greater locally.
It all depends. It's true that locally-sourced applications & locally-stored data could potentially be unavailable from long-term outages or hardware issues...but cloud-based services don't prevent that. Your office has no power? Guess what: your router & other hardware for connecting to the Internet (not to mention the PCs) are all offline. Hard to connect to a cloud provider without Internet or a device.
And then, of course, there's the issue where your location has power & Internet, but maybe the cloud-storage data center is offline because they're having a local power outage. Or worse, if a natural disaster (or a man-made disaster) happens & takes out the data center, you'd better hope & pray that the provider has another data center available, or you're pretty far up the creek.
Google Docs is inaccessible once in xx number of years and suddenly the "local only" crowd is blitzing the forums and ripping anyone who doesn't agree with them. Calm down folks, you all work too hard anyway. Maybe an outage vacation will let you have a break!