I found an example (http://www.betweentherails.com/rake/) of passing
arguments to a rake task in the new (0.8.n) version of rake. From this
example, I created the following test:

namespace :foo do
  desc 'lol'
  task :bar, :num do |t, args|
    puts "num = #{args.num}"
  end
end

I took a look at the task list:

$ rake --tasks
(in /path/to/my/dir)
rake foo:bar[num]  # lol

All looks well ... until I try to run it:

$ rake foo:bar[123]
rake: No match

Hmm ..  let's try without the argument:

$ rake foo:bar
(in /path/to/my/dir)
num =

o.O