I never had. First it would slow things down and I keep sensitive stuff off my comuters.
encryption is your friend.... I use full disk encryption, EFS and truecrypt....
I think it is a terrible idea and it will almost certainly wreck your operating system. IMHO encryption should be used only under the following circumstances:
For sensitive data files.
If you are fully familiar with file encryption techniques, key files, backup and restore issues.
Data-encryption alternatives to TrueCrypt - by Lincoln SpectorQuote:
Full-drive encryption makes the most sense if you work primarily and continuously with sensitive information — as in accounting. In most cases, an encrypted partition makes more sense; it’s nearly as secure as full-drive encryption and offers more flexibility. File-by-file encryption is the least secure but is worth considering if you can’t use drive/partition encryption
don't think it matters
Full-disk. Unless you have a specific reason for encrypting individual files--such a financial statements or legal documentation that may get moved around.