"The seemingly innocuous romantic gesture also occurs at the Ponte Vecchio in Florence, the Ponte l’Accademia in Venice, and less renowned bridges in Liverpool, Hamburg and many other romantic locations in cities throughout the world.A simple Google image search shows the scale of the problem. Aesthetically and emotionally it's an extraordinary sight but intellectually I can't not imagine the danger.
"The situation in Paris has become more critical, though, and according to local newspapers, the Paris Council worries that so many padlocks have been snapped on the Pont des Arts that the railings risk crumbling under the weight and crashing into the river. The scenario some of them fear is not only of people tumbling into the river along with the railings but of the heavy metal enclosures landing on passengers on the many tourist boats that ply the river under the bridge."
Technology Some of Paris's bridges are under threat. Not from rot or decay or the kinds of thing you might expect, but from ritual, specifically the ritual of lovers inscribing their names on padlocks, clipping them to available railings and then throwing the keys in the Seine: