categorization has_many :through should have an ID, and the relationship should be destroyed if the blog post or category is

app/models/blog_category.rb

@@ -1,6 +1,6 @@
 class BlogCategory < ActiveRecord::Base
 
-  has_many :categorizations
+  has_many :categorizations, :dependent => :destroy
   has_many :posts, :through => :categorizations, :source => :blog_post
 
   acts_as_indexed :fields => [:title]

app/models/blog_post.rb

@@ -13,7 +13,7 @@ class BlogPost < ActiveRecord::Base
   has_many :comments, :class_name => 'BlogComment', :dependent => :destroy
   acts_as_taggable
 
-  has_many :categorizations
+  has_many :categorizations, :dependent => :destroy
   has_many :categories, :through => :categorizations, :source => :blog_category
 
   acts_as_indexed :fields => [:title, :body]

db/migrate/1_create_blog_structure.rb

@@ -30,7 +30,7 @@ class CreateBlogStructure < ActiveRecord::Migration
 
     add_index :blog_categories, :id
 
-    create_table :blog_categories_blog_posts, :id => false do |t|
+    create_table :blog_categories_blog_posts, :id => true do |t|
       t.integer :blog_category_id
       t.integer :blog_post_id
     end