With the arrival of iOS 4.2, iPhone 4 users can create a free MobileMe account to use the Find My iPhone service, however, Apple has limited the number of free accounts to 3 per device. If we exceed this number we will get the following message:
Account limit has been reached.
This device does not have the ability to create more free MobileMe accounts.
Be careful all those who plan to create multiple accounts.
Source: TiPb