CFLs burn out rapidly when they’re not allowed to rest at least 15 minutes between being cycled off and on. They overheat and fail if they are used in recessed ceiling canisters
CFL floodlights in outdoor motion-sensor systems is bad because of how fast the bulbs expire when they have to flick on and off so quickly. CFLs contain mercury, enough that the Environmental Protection Agency’s cleanup instructions for a broken bulb run three pages and start with a warning to open windows and evacuate people and pets.