Lets talk about a few factors of overspeed, including the recent couple of events being discussed on other threads.
How many total events have occurred in the last 30 years?
Which configuration of constant speed propellers experienced overspeed? (all propellers were non counterweighted type? increase oil pressure to hub increases blade pitch)
What was the final determined cause? (usually governor?) (Which brands?)
How high did the RPM get? High enough to damage engine equipped with non counterweighted props? Propeller damaged also?
Damage to accessory drive gears and possible the crank gear / bolt & pin? (due to seized governor shaft?)
What was the pilot's reaction? (close throttle quickly?, Climb steeply to reduce airspeed?)
I agree automatic protection devise(s) might be a good idea, especially when they are included as a 'feature' as in an electronic ignition or electronic fuel injection or full electronic injection + ignition systems. These don't seem prone to causing engine shut down in normal use, which would be unacceptable. (Failure mode analysis) Obviously these reset when engine speed decreases to normal.
Counterweighted props are preferred for aerobatics, because loss of oil pressure to the propeller causes increased pitch. one poster did have a governor failure on a counterwieghted prop equipped IO-540. No overspeed, but he did lose over a quart of oil in about 10 minutes and may have had accessory gear damage.