Locking down Apple's new Find my iPhone / iPad

Kudos to Apple for making this service free, it's well worth enabling.
However to make sure you're properly protected there are a few changes
you should make in Settings.

Enable Passcode Lock and, optional but recommended, Auto-Lock.

Next enable restrictions and disable deletion of apps and accounts.
This will prevent thieves from nuking your MobileMe account or your
Find my iPhone / iPad app.