There was a post a few years ago that detailed many of the archaic and somewhat obscure requirements that boarding passes must have: http://blog.timoni.org/post/318322031/a-practical-boarding-p...

It seems as though Virgin America can bypass many of these because there are no (?) international flights.

The original boarding pass redesign post, to which the above was a rebuttal: http://passfail.squarespace.com/

Edit: wrong links.