No, seriously - depending on the cloud service, aren't buckets of data encrypted in such a way that only the owner of the data can access them? Cloud service providers may be required to hand over data, but do they have the means of handing over the encryption keys along with it?
For certain cloud services where you're uploading via browser, they may be encrypting your data post-upload, so the request to decrypt may be more trivial. However, if you manage your own (like S3 backups) - or simply use a service that encrypts BEFORE uploading, I'm not sure there's a whole lot Amazon or some other provider could do to hand over the data in any usable form.
Those who are concerned about security of their data should ensure that the backup is encrypted in an acceptable method, or simply stash it in an encrypted container before storing it "online" (I realize there may be limitations of scale with that suggestion).