I'm rubbish at getting around to things. Back in January, adactio linked to a video about making dead-drops saying "I should get out there and make a few drops in Brighton". A few days later he posted a flickr set, dead drops in Brighton, showing him with wordridden and briansuda setting up some USB dead-drops. There was also a map to the locations. (For more information, there is some background/discussion of USB dead-drops on metafilter, as well as a catalogue website).
This weekend, about 2 months later, I finally got round to checking the dead drops with Vicky Matthews (who took the photo below). It was a sad story.
We only found the location of one of the two seafront drops. As Pier-to-pier complained frequently, salt air is no good for hardware, and the drive was too corroded to read: