You know those obnoxious locks that litter bridges, as a supposed sign of people's love? I wrote a bit of a rant about them here.
Here is one more reason they are a bad idea: they just caused part of a railing on a Paris bridge to collapse. Read more here.
They also damage the bridges, causing them to rust faster. People need to start thinking about the consequences of their actions. If they feel some sort of need to make a spectacle of their affection, how about doing something productive? For example, when an organization is trying to raise funds, it will often sell engraved bricks. Buy one of those. Don't put other people at risk because of your actions.