The Blog Ride thinks that dynamic languages provide power that most people just can't handle:

Folks, we need to realize something: all this "expressiveness" is like putting craftsman's tools in your hands; in the hands of a master craftsman, amazing things can result, but in anybody else's hands, it's putting a loaded gun into the hands of a child. YOU may be good enough to be disciplined enough to keep the rules of your types in your head when programming with Ruby, but are all of the programmers on your team equally gifted? Are all of the programmers that will follow you so gifted?

I think David Buck's latest post explains what's at stake quite nicely. To my mind, it's all about just how much productivity you are willing to sacrifice in the name of presumed safety.