.Mac sync doesn't work without saving your password in the Apple Keychain -- BROKEN! I don't want to save my password on a laptop that's likely to get stolen.

If you delete your .Mac password from the keychain, Sync Now from the iSync menu fails with an error, but without an opportunity to enter the password:

Menu: Sync Now Error

In System Preferences:.Mac:Sync, clicking Sync Now generates the same error message with a different icon:

System Preferences: Sync Now Error

After entering a password in System Preferences:.Mac:Sign In, the system pops up a keychain password prompt. If a password is provided, the .Mac password is immediately saved to the default keychain. This is the only keychain access dialog I'm aware of which doesn't offer a checkbox to save the password, and instead forces password saving on -- BROKEN!:

.Mac Keychain Password dialog

No .Mac renewals for me.