README.md in simple_cacheable-1.3.1 vs README.md in simple_cacheable-1.3.2

@@ -41,13 +41,18 @@
 
       belongs_to :user
       has_many :comments, :as => :commentable
 
       model_cache do
-        with_key                          # post.find_cached(1)
-        with_association :user, :comments # post.cached_user, post.cached_comments
+        with_key                                # post.find_cached(1)
+        with_class_method  :default_post        # Post.default_post
+        with_association   :user, :comments     # post.cached_user, post.cached_comments
       end
+
+      def self.default_post
+        Post.first
+      end
     end
 
     class Comment < ActiveRecord::Base
       include Cacheable
 
@@ -64,9 +69,17 @@
 add the following code to your Gemfile
 
     gem "simple_cacheable", :require => "cacheable"
 
 
+Gotchas
+-------
+
+Caching, and caching invalidation specifically, can be hard and confusing.  Simple Cacheable methods should
+expire correctly in most cases.  Be careful using `with_method` and `with_class_method`, they should
+specifically not be used to return collections.  This is demonstrated well Tobias Lutke's presentation: [Rockstar Memcaching][2].
+
 Copyright © 2011 Richard Huang ([e-mail]), released under the MIT license
 
 
 [1]:https://github.com/flyerhzm/rails-bestpractices.com
+[2]:http://www.infoq.com/presentations/lutke-rockstar-memcaching