Google's data centers are slightly more reliable than the average laptop hard drive.

But are they as reliable and available as a laptop and a USB stick? That's a hard one to prove.

I assume they make back-ups all the time, so yes. Definitely more reliable for most people.

That's a pretty big assumption, for example:

http://www.theregister.co.uk/2012/05/09/atlassian_cloud_stor...

But what if there's a bug where attackers gain access to your account and drain all of your Word documents into their bank accounts!!!11?