What's the proper (seo safe) way to blackout a site (e.g. for SOPA)? I want to safely blackout my Drupal site to raise the awareness of SOPA. What's the SEO friendly way to do that?

I'm thinking of putting my site into maintenance mode and just changing the maintenance message.
I found this post on the Drupal Google+ page. It says:


  Black out your #Drupal site against #SOPA on Wednesday. Drupal's maintenance mode is 503 status so it won't hurt your SEO.