Just found this, looks like Katz thinks everything should be in the gemspec, so long as it's not a gem that's not up on Rubygems yet. http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/ 

Like it makes sense to add_development_dependency('rspec') because the tests are written in rspec. That way, it also shows up on Rubygems as a development dependency. Just tossing the idea out there though, just seems strange to have them in both places.