I trust more Apple than Google but I would never put my stuff unencrypted on their servers.
Imagine all the data Google has on their Google Docs. They might know a lot about companies and even governments worldwide since there's too many people who
don't care about their privacy. Why they offer so many good services for free? So they can use your personal information to sell ads. The problem relies when ONE company has all that data.
Many people think they don't have anything to hide so it's not big deal. You never know who might have access to data related to you. Could be some totalitarian government (search for Tibet in China and you go to a special list) or some adversary (some company's competitor), etc.
Nothing to hide? Could be family pictures, bank statements, medical records, contact addresses, important company documents, etc.
I don't want to sound paranoid but common sense says you should encrypt your files before uploading them to a public server.
I use TrueCrypt with DropBox. Both are free.
A website people should check:
https://ssd.eff.org