I wonder if that would make people drive progressively faster over a stretch of road until they notice the bump.

Or more common, people will speed towards the bump and again, brake right before it.

...and the neighborhood Concerned Mothers Association (TM) that worked so hard to get the town to install them will then start complaining when they have to listen to every motorcycle and riced out Civic accelerate after the bump.

Which can reduce damage of delicate loads, like ambulances. I expect it would reduce wear-and-tear on suspension of heavy vehicles too.