For example...A USB (Universal Serial Bus) stick with classified military documents [1]on NATO's ISAF peace-keeping force in Afghanistan, as well as an intelligence report on the attempted assassination of Lebanon's defense minister and the murder of Sri Lanka's foreign minister. These items were found at a public library in Stockholm, Sweden; no one is exactly sure how the USB stick ended up on a public computer at the library.

Here's the original report [2] in Swedish and more from the AP [3].