Interesting article at Scientific American
: "How the iCloud Hack Happened and How to Avoid Being Next" by Paul Wagenseil and SecurityNewsDaily (August 7, 2012).
....."What happened to me exposes vital security flaws in several customer-service systems, most notably Apple's and Amazon's," Honan wrote in a long piece published on the Wired magazine website last night (Aug. 6). "Apple tech support gave the hackers access to my iCloud account. Amazon tech support gave them the ability to see a piece of information — a partial credit-card number — that Apple used to release information.
....."In short, the very four digits that Amazon considers unimportant enough to display in the clear on the Web are precisely the same ones that Apple considers secure enough to perform identity verification."