namespace :items do
  desc "Spider the web for data, hoorah"
  task :spider => :environment do
    Item.spider!
  end
end

$ rake items:spider RAILS_ENV=production --trace
(in /home/matchu/Websites/my-rails-app)
** Invoke items:spider (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute items:spider
rake aborted!
uninitialized constant Object::Item
/home/matchu/.rvm/gems/ruby-1.9.2-preview3@rails3/gems/rake-0.8.7/lib/rake.rb:2503:in `const_missing'
/home/matchu/.rvm/gems/ruby-1.9.2-preview3@rails3/gems/rspec-core-2.0.0.beta.22/lib/rspec/core/backward_compatibility.rb:20:in `const_missing'
/home/matchu/.rvm/gems/ruby-1.9.2-preview3@rails3/gems/rspec-expectations-2.0.0.beta.22/lib/rspec/expectations/backward_compatibility.rb:6:in `const_missing'
/home/matchu/Websites/openneo-impress-items/lib/tasks/items_spider.rake:4:in `block (2 levels) in <top (required)>'
/home/matchu/.rvm/gems/ruby-1.9.2-preview3@rails3/gems/rake-0.8.7/lib/rake.rb:636:in `call'
[...trace of how rake gets to my task...]

module Rails
  class Application
    module Finisher
      # ...
      initializer :eager_load! do
        if config.cache_classes && !$rails_rake_task
          ActiveSupport.run_load_hooks(:before_eager_load, self)
          eager_load!
        end
      end
      # ...
    end
  end
end

Rails.application.eager_load!

config.dependency_loading = true if $rails_rake_task