Less is More - Dynamically typed languages

When I was in the university I learned that strongly typed languages should be preferred since they avoid the programmers from using a certain variable in way that it was not meant to.
If I declare "string name;" I know this will accept only strings and will prevent a programmer from assign a number or a boolean value on it.

But this seems to be a false concern with the success of other languages such as Python and Ruby.
This programming languages are now used to each time more complex software and nobody is complaining about their "dynamic" features.

The goal the new development tools are trying to achieve is how can I do my software faster in a clean and organized way. Less is More !