Do not check class collisions, we want to be able to scaffold and then apply Devise on top of it.

generators/devise/devise_generator.rb

@@ -4,9 +4,6 @@ class DeviseGenerator < Rails::Generator::NamedBase
 
   def manifest
     record do |m|
-      # Check for class naming collisions.
-      m.class_collisions(class_name)
-
       # Model
       m.directory(File.join('app', 'models', class_path))
       m.template 'model.rb', File.join('app', 'models', "#{file_path}.rb")

generators/devise/templates/migration.rb

@@ -1,7 +1,7 @@
 class DeviseCreate<%= table_name.camelize %> < ActiveRecord::Migration
   def self.up
     create_table(:<%= table_name %>) do |t|
-      t.authenticatable :encryptor => :sha1
+      t.authenticatable :encryptor => :sha1, :null => false
       t.confirmable
       t.recoverable
       t.rememberable

lib/devise/schema.rb

@@ -8,17 +8,11 @@ module Devise
     # == Options
     # * :null - When true, allow columns to be null.
     # * :encryptor - The encryptor going to be used, necessary for setting the proper encrypter password length.
-    # * :skip_email - If you want to use another authentication key, you can skip e-mail creation.
-    #                 If you are using an ORM where the devise declaration is in the same class as the schema,
-    #                 as in Datamapper or Mongomapper, the email is skipped automatically if not included in
-    #                 authentication_keys.
     def authenticatable(options={})
-      null = options[:null] || false
+      null       = options[:null] || false
       encryptor  = options[:encryptor] || (respond_to?(:encryptor) ? self.encryptor : :sha1)
-      have_email = respond_to?(:authentication_keys) ? self.authentication_keys.include?(:email) : true
-      skip_email = options[:skip_email] || !have_email
 
-      apply_schema :email,              String, :null => null, :limit => 100 unless skip_email
+      apply_schema :email,              String, :null => null, :limit => 100
       apply_schema :encrypted_password, String, :null => null, :limit => Devise::ENCRYPTORS_LENGTH[encryptor]
       apply_schema :password_salt,      String, :null => null, :limit => 20
     end