Where we live you can't leave the poop in the yard for more than a week (city bylaw) so we pick up every day - means less mines for the mower!! As for picking up in Winter - I find it much easier to pick up from the snow than the grass.
I've often wondered about that too - guess they are relying on your neighbours to report you...How does the city know if you've waited over a week to clean up? Just curious.