I've got a bit of a pet peeve about these. It seems everytime I go for a ride, I'm finding them in the bike lanes. I know bicyclist don't like having trash or debris in the bike lanes so WHY THE HECK do they leave their CO2 cartridges there??? They have carried them that far, can't they just carry them back and dispose of them in a trash can somewhere. They are a hazard, just like anything else in the lane. Weight weenies or not, it's stupid to leave them there! If I stopped everytime I saw one in the bike lane and picked them up, I would be stopping quite often. Next time out (today) I might just start stopping and picking them up just to see how many I collect on one ride.