title: Rails model structures
body: <p>I saw some threads on this already on Stack, but wanted a little more clarification.</p>
  
  <p>I have seen many apps where there is a product model and category category model.  This is a has and belongs to many association, or a has_many through association.</p>
  
  <p>I have also seen many apps where there is a user model and an email_address model.  Email_address belongs to user, but user can have many email addresses. </p>
  
  <p>My question is, would there ever be a situation where you can lump all the email addresses or categories into the user and product models, respectively?  So in your user model, you will have email_one, email_two, etc?</p>
  
  <p>What are the pros and cons of breaking it into different models?  Thanks.</p>