I think we have to distinguish between stealing and cloning here. If someone steals the scrap of paper you wrote your key on, then you will know. And passport

I think we have to distinguish between stealing and cloning here. If someone steals the scrap of paper you wrote your key on, then you will know. And passports do get cloned; the issue is convenience. 1. http://www.independent.co.uk/news/uk/home-news/clone-wars-mossads-london-chief-expelled-over-forged-passports-1926147.html http://www.independent.co.uk/news/uk/home-news/clone-wars-mo... 2. http://www.expatsvoice.org/forum/showthread.php?t=7001 http://www.expatsvoice.org/forum/showthread.php?t=7001 I guess that Mossad can gather the information needed to clone a passport in under half a minute. So while I agree that the analogy between key reminder and password is not perfect, the point is basically sound. (On rereading your post, your point [p]hysical items also need to be carried to a destination to be used made me realise that I might have misunderstood the point you were making, but also that you may have misunderstood the point ihodes was making).