While in Paris I took a tour that went off the beaten path to explore the bohemian side of the city. The tour was with Urban Adventures and I would do it again in a heart beat. At one point in the tour we came across a bridge full of locks and the tour guide explained that this is a bridge where lovers would place a lock written with their name and their soul mates name. Then they would throw the key into the river. This symbolizes that their love can never be unbroken or unlocked.
Later as I was strolling on the sidewalk I saw vendors who had locks available to sell to whoever wanted to take part in this ritual. I'm sure these people must get awfully rich around Valentines day :)
After I got home I did further research on this fascinating ritual and stumbled across this neat article on the Paris love locks entitled: Paris Love Locks: A Love that Won't Die