Pad Lock

What is the deal with the lock on the bridge Sforezco Park?

In Sforezco Park behind the castle of Milan, a small bridge spanning a small pond. The bridge is composed of several nodes enormous padlock. Does anyone know the meaning or symbolism of them?

This is seen in many places here - is a declaration of love that comes from a book and film (Ho voglia di te - http://www.imdb.com/title/tt0877522/). You write their name on the block, blocking, and throwing the key into the water. There is an article in the International Herald Tribune, which explains in more detail here (in Regarding the bridge of Rome): http://www.iht.com/articles/2007/08/05/africa/rome.php. You can find several versions of the same product with different images, eg http://www.1millionlovemessages.com/2008/02/rome-a-new-ritual-on-an-old-bridge.html