Informative article, thanks!
However, regarding your comment,
The key point here is that the iMessage content would be available in backups.
As of iOS8, iMessages are encrypted end-to-end, meaning that even with the iCloud backups, without the endpoint (the iPhone) password, it cannot be decrypted.
See the “iMessage and Facetime” section on this page for details: http://www.apple.com/privacy/approach-to-privacy/
…we wouldn’t be able to comply with a wiretap order even if we wanted to…
UPDATE: as Mike pointed out below, if you enable iCloud Backup, then Apple will have access to your iMessages. So the original post is correct.