What do pairs of shoes on the side of the road mean?

I drive the same road everyday and there is an unusually high amount of shoes on the side of this road. Its not just 1 random shoe without a mate either, its PAIRS. Sometimes, well most of the time, the are setup there neatly side by side. The same pair(s) will stay there for a couple of days then theyll just disappear and new ones will popup at a different part of the road. All different kinds too, kids, adults, dress, casual, summer, winter, sandals, boots, etc etc. Its only on about a 1 mile stretch and its not somewhere where people go hiking or hunting or anything like that. As a matter of fact the shoulders barely big enough to stand on and its a windy dangerous road. Im so baffled as to whats going on here and would really like to figure it out. Somebody told me that it might have something to do with drugs (liek the telephone wire thing). Im just really curious about this because ive never seen it before. Thanks!