The first time that I heard about Dead Drops, I was intrigued by the idea behind them. Offline public file sharing using USB thumb drives that were built into buildings; but then I realized how bad this idea is from a security stand point. Auto run scripts, viruses with images in them, etc. could very easily be planted in these thumb drives and then installed on an unsuspecting machine. The faq page at deaddrops.com suggests to use a virtual machine to read the drive, but even then it is not always easy to tell whether or not the USB port is directly sent to the virtual machine or if the data first gets sent to the host OS. If the latter, this is not any more secure than no virtual machine. Another option is to use a machine that is dedicated to connecting to Dead Drops. This works as long as it stays dedicated to Dead Drops. Even then though, if the Dead Drop isn’t actually a real Dead Drop and is actually connected to 110v wall power (for example), good luck trying to fix your computer.
[EDIT: After I posted this I was checking xkcd and the current one is relevant- http://www.xkcd.com/956/]
Image above credited to Aram Bartholl (Creative Commons By-NC-ND).