“Find My iPhone” requires an Apple ID that is an email address

When I tried to activate “Find My iPhone” (FMi), I got the error message “MobileMe requires an Apple ID that is an email address”. This is how I fixed the problem:
  • Old Apple IDs are just a name like “smith”, not an email address like “smith@example.com”.
  • You can go to your account settings in iTunes and change this name to an email address so that FMi won’t complain, any more.
    • However, when I tried to do so, I found out that I had a very old account (that I had never used on iTunes) whose name was that email address. Thus, I could not rename the original account.
    • You cannot easily delete accounts, so I logged into the old account, had to enter my credit card information (grrr!), and then could change its name to something completely different.
    • Now my email address was free and I could switch to it at the original account.