https://github.com/travis-ci/travis-crowd/blob/master/script/followers.rb – no Twitter gem

evil.rb

require 'open-uri'

twitter_url = "https://api.twitter.com/1/followers/ids.json?screen_name=%s"

follower_ids = %w(travisci joshkalderimis konstantinhaase svenfuchs).map do |screen_name|
  Array(eval(open(twitter_url % screen_name).read.match(/"ids":(\[[0-9,]+\])/)[1])) rescue []
end.flatten.uniq

puts follower_ids.length

json.rb

require 'json'
require 'open-uri'

twitter_url = "https://api.twitter.com/1/followers/ids.json?screen_name=%s"

follower_ids = %w(travisci joshkalderimis konstantinhaase svenfuchs).map do |screen_name|
  Array(JSON.parse(open(twitter_url % screen_name).read)['ids']) rescue []
end.flatten.uniq

puts follower_ids.length