@johnf's code that reproduces the stack level too deep error on ubuntu 12.04.2 vm on esx comment out the [1].each do on line 42 and the problem goes away. I think defs foo and bar are not required to trigger the error.

test.rb

#!/usr/bin/env ruby

require 'eventmachine'
require 'em-synchrony'
require 'thin'

#require 'thin/version'
#module Thin
#  def self.win? # Are we runing windows
#    true
#  end
#end

Myapp = lambda { |env| [200, {}, 'this is my app!'] }

module Flapjack

  module Pikelet

    def self.create
      [Flapjack::Pikelet::Thin].each do |kl|
        kl.create
      end
    end

    class Thin

      def self.create
        self.new
      end

      def initialize
        p caller.length
        foo
      end

      def foo
        bar
      end

      def oath
        [1].each do
          @server = ::Thin::Server.new('0.0.0.0', 3000, Myapp, :signals => false)
        end
      end

      def bar
        oath
      end

    end

  end

  class Coordinator
    def start
      EM.synchrony do
        add_pikelets
        puts "WIN"
        exit
      end
    end
    def add_pikelets
        Flapjack::Pikelet.create
    end
  end

end

coordinator = Flapjack::Coordinator.new
coordinator.start