The more dynamic (powerful?) the language the more leverage good, experienced developers have. They can achieve results in 10 lines of code that are hard/impossible in more static languages (closures, meta-classes etc.). The other edge of the sword is that one dud developer can bring your whole stack down by being too smart for their own good. The more dynamic the system the greater the risk. In Ruby as is pointed out you can have a developer on the other side of your code base royally screw you because he wants feature X of sequences to act differently.
As with all things it's a balancing act, how smart are your devs, how much time can you spend testing and how strict are your coding standards.