The right balance really depends on your domain. The reason I'm so big on dynamic typing is because the most important part of the product I work on is a ton of reporting from an SQL database. I shift as much work as possible to the database, so the results that come back don't need to be unpacked into some domain model but are ready to go for outputting to the user. If I tried to do this in a static language I'd have a new type for every single query, then have to convince my various utility functions to work with my type zoo.
