Slightly off-topic, but since the thread seems to be veering in that direction...
I think a lot of the problems people have with rattle cans are user based, mostly from not following the directions on the can. (For some reason, a lot of people have a stubborn need to ignore them, but I digress....)
1. ACTUALLY shake the can vigorously for at least the 1 minute the instructions usually recommend, and keep shaking between coats.
2. ACTUALLY wait the recommended recoat and dry times.
3. ACTUALLY paint in the recommended temp and humidity ranges.
4. Clean the nozzle when you're finished.
5. If you want a bit of insurance, leave the can in sunlight or warm water for a few minutes before use.
I think a lot of spray paint problems would be avoided by using the manufacturers recommended usage steps. It's why they're there, after all.