I understand your point but many people do leave their cars in dark
places at night and they don't lose their OEM stereos.

I think some people just remove the faceplate and put it in the glove
box.  How many people actually take the stupid faceplate with them when
they leave their cars?  With removable faceplates, you're just waiting
for someone to try and nick it or drop the stupid faceplate or have
some other accident with it.  Of course, there's the other stupid
situation where you get in the car only to remember you've left the
faceplate somewhere.  It's not a good security system.

Only had one stereo stolen from a car (not my 320, my old Rover 214). Midday
Sunday, broad daylight, across the road from terraced houses, and nobody saw
a thing. They must have been in and out fast - I was only away from the car
for 30 mins, and I came back to find wires hanging out of the DIN slot,
screwdriver marks all around it, and my sunglasses missing too. It was the
first, and last time, I'd forgotten to take the front off the stereo. Still
didn't stop someone else breaking into it a month later outside my house
while I was at work (crank seal had blown out so the car was immobile for 2
days while waiting for a mechanic friend to take a look at it) despite the
wires hanging out of the dash making it blindingly obvious there wasn't
anything worth stealing.

And to top it all off the local police station was closed, and report I
filed online (for the original theft) never got followed up - at least the
contact I was supposed to have received within 2 working days never
occurred.

Dan