gistfile1.rb

class User
  include Mongoid::Document

  [:street_address, :phone_number, :email_address].each do |f|                                                                         
    embeds_many f.to_s.pluralize.to_sym do                                                                                             
      def [](key)                                                                                                                      
        detect {|e| e.name.eql?(key.to_s)} || build(:name => key.to_s)                                                                 
      end                                                                                                                              
    end                                                                                                                                
    define_method f do                                                                                                                 
      send(f.to_s.pluralize).send('[]', :primary)                                                                                      
    end                                                                                                                                
  end  
end

:001> u=User.new
 => #<User _id: 4f14134a0096044a70000001, _type: nil >
:002> u.email_address
=> #<EmailAddress _id: 4f1966a50096046eb7000003, _type: nil, name: "primary", email_address: nil>
:003> u.email_addresses[:secondary].email_address = '[email protected]'
 => "[email protected]" 
:004> u.email_addresses
 => [#<EmailAddress _id: 4f1966a50096046eb7000003, _type: nil, name: "primary", email_address: nil>, #<EmailAddress _id: 4f1967120096046eb7000004, _type: nil, name: "secondary", email_address: "[email protected]">]