Just a quick everyday complaint. It is very annoying to go around the gym trying to find the dumbbell weights you need or stepping over plates that people have left because they are too lazy to put them back on the rack.
Gym etiquette and for that matter general basic etiquette. If you take something, put it back. I think gyms should enforce this. Ban them, cancel their memberships, send them packing. Maybe a little too extreme but something should be done with those who are too inconsiderate and lazy to do something so simple. Re-rack your weights!