James...

some thoughts..

a) Most cops don't know what speed the spoiler deploys...most probably don't know it deploys at all.

b) The spoiler can be manually deployed at any speed, so right there it invalidates the assumption of a deployed spoiler equals speeder.

c) Once the spoiler is deployed, it does not retract itself until just below 40 mph, so again seeing a spoler out might suggest that someone did go above a certain speed, but it does not mean it's being maintained.

d) Fixed spoiler equaling more downforce. Downforce is not needed all the time, actually on the highway downforce generated by a large wing is rarely 'needed', and when not needed it actually creates drag/lowers fuel economy.

I'll stick with the tasteful retractable than the butt ugly fixed wing.