title: Rails persisted locale
body: <p>I'm about to start adding I18n support for a Rails app I'm currently working on. In the past I have set the locale value from the URL. I just was wondering how bad practice it'd be to persist the locale?</p>
  
  <p>So instead of something like this:</p>
  
  <pre><code>before_filter :set_locale
  
  def set_locale
    I18n.locale = params[:locale] || I18n.default_locale
  end
  </code></pre>
  
  <p>Do something like</p>
  
  <pre><code>before_filter :set_locale
  
  def set_locale
    I18n.locale = current_user.try(:locale) || I18n.default_locale
  end
  </code></pre>
  
  <p>It looks like FB persists the locale, what are the trade-offs of this schema? how might this affect SEO stuff?</p>
  
  <p>Thanks!</p>