once - in Macau, lost my iPhone 3G. It was picked from the outer pocket of my backpack... as I exited from the ferry terminal immigration a bunch of guys rushed into my face asking if I wanted to take this or that tour, within 45 or so seconds I managed to tell them to get away but the job was done, looked around to discover my backpack unzipped and the phone gone!

My mistake for: 1) putting anything of value in the outermost backpack pocket 2) Not locking my backpack 3) Not being on guard when people approach me like that

well...live and learn!