A little help here?

Walking around the Adams-Morgan neighborhood the other day, near Rock Creek Park, I came across these locks attached to a fence on a street bordering the Park:

Here's a close-up of one of the locks:

There's a lovely little tradition in Italy (and, I think, elsewhere in Europe as well) whereby couples, to declare their ever-lasting love (hah!), attach locks onto bridge walkways. [The most famous is probably the Milvian Bridge over the Tiber in Rome - yes, the very same Milvian Bridge that was the site of Emperor Constantine's famous conversion to Christianity in the 4th Century A.D., surely one of the more important moments in the history of Western Civilization]. From a distance, that's what I thought was going on here - although on closer inspection it was clear that something else was happening, and these were not "lover's locks"

But what are they doing there? What's going on? Any ideas?