If you love somebody...

 ...set him free! 
From every point of view, I find this habit of the locks on bridges, not to my taste. 
First, it's not good for the environment, second, it's too much weight for some bridges, third, it's simple, if you love somebody don't lock him or her, set them free.
Anyway, it seems that many people in Europe consider it romantic and they keep doing it.