Had a good example of this last Tuesday. We were out south of the city childminding at my youngest boy's house. Rained pretty much all day and still raining when we left to go home.
So, up to the top of the hill and onto the main road which leads past the filling station. Building up to 30mph, which is the limit here, with a large SUV trying to "push" me to go faster, when suddenly realize that what looks at first like just a very wet area of road surface is actually a very large area of flooding covering most of my side of the road. I braked quite firmly, not what you'd call emergency braking though, and was very nearly rear ended by the SUV who was obviously not expecting me to slow on this bit of straight road and had been caught out because they were following far to close. Must have been within a foot of my rear bumper before getting themselves properly under control again, thank goodness for ABS?
Thankfully no harm done, except perhaps the driver needing a change of underclothes, but all could have been easily avoided by following the "only a fool" rule. Glad I slowed though, the water was almost up to the wheel hubs!