In Mostly Harmless, Douglas Adams wrote about a fantastic device: an identification card that stored every conceivable piece of information about its owner. It would function to give universal access to anything the owner ever had access to. Passwords, ID numbers, fingerprints, retinal scans, it was all in there. The function of the device was convenience; the problem was that, if it were stolen, then anyone anywhere could easily impersonate the cards owner.
Silicon.com mentions a real-world equivalent, an ID card that could store everything possible about a person. Again, the main benefit of the card would be convenienve. And again, the danger of the card is that it could be lost or stolen.
I think that Douglas Adams needs to be required reading in schools nowadays. Perhaps it would help people see when they are making a fundamentally unsafe product, such as this ID card.