Dropbox is a good service, and I am sure file access is limited to a few employees, but I wouldn't use it for sensitive data or for a business. Any service where you do not control the encryption keys, e.g. Box.net, and myriad others will have the same issue. It's all about tradeoffs. Ultimately they can access your data. The truecrypt option may solve it for some but that means the whole archive has to be shared.

AltDrive unlimited online backup versions your files and allows you to control your encryption key. It runs on *nix, OSX, Windows, and other OSs. http://altdrive.com