[malyk]

And you'd never know that they existed if you look at the user model...

My stance is that things like sending email should be explicit calls so they are obvious. Sending email when registering a new user, for example, should be in the if user.save branch in your controllers or, if you have a more SOAish app, in the service that creates users.

def create user = User.create(params[:user])

  if user.save
    Emailer.new_user_email.deliver
    render 'welcome'
  else
    render 'oh shit'
  end

end

Or, refactor that out a bit (ONLY IF NECESSARY!)

def create user = UserService.create_user_from(params[:user])

  if user
    render 'welcome'
  else 
    render 'oh shit'
  end

end