In LA, it appears you're more likely to get ticketed for just the no-front-plate in an area where there are red-light camera, or some other similar reason (LAX, anyone?). I've been driving all my cars front plateless for 7 years, have even gotten 2 speeding tix in that time, and no citations for the plate.
Because front plate laws often specify placement limits, certain techniques such as sticking it on your dash doesn't make it legal, either. What a few friends of mine who are in high-ticket areas do is keep their front plate in the car with butyl tape stuck on the back, and slap it on their bumper when parked in those areas.