The act of locking away your love does seem like a romantic gesture... and to do this with your lover in the most romantic city in the world might seem like a good idea. However, the Parisians aren't so happy with it. Not only is it ruining the architectural integrity of the Parisian landscape... but according to the locals, we're missing the whole point of what love truly means. Here is a quote I found when trying to figure out why there were locks on the bridges: "At the heart of love à la française lies the idea of freedom. To love truly is to want the other free, and this includes the freedom to walk away. Love is not about possession or property. Love is no prison where two people are each other’s slaves. Love is not a commodity, either. Love is not capitalist, it is revolutionary. If anything, true love shows you the way to selflessness."
If you happen to be visiting Paris with your significant other and were thinking about buying one of those padlocks, I would think twice about what your motives really are.