If you use Google Office Applications, check out gdatacopier. One of my only complaints about using Google Documents has been having to manually export and backup my online documents - now, problem solved.
Although there is some sensitive information that I would not store in Google Documents, for most information having it online and available is a deal maker for me - I also like being able to share specific documents for group writing.
There is a question whether storage and software services should be "outsourced". For most of my business and research interests, I would answer that question with a "yes". For me the issue is in reducing labor costs. By using leased managed servers, Amazon EC2/SimpleDB/S3, Google Data, DabbleDB, etc. does precisely this: it allows systems to be run and maintained much more inexpensively by outsourcing infrastructure.
One firm requirement for outsourcing infrastructure is a plan for recovering from the loss of an outsourced service. Such a plan must include periodic data backups under your own control as well as a strategy for duplicating services - not always easy to do.