Was the guy not properly screened? If he was, then there was no breach of security. The airline may have been risking a fine for transporting someone inadmissable to the destination country, but that's about it.

As long as someone has passed thru the WTMD and had an x-ray of their bags, then I'll be happy to sit next to them, even if it's Osama Bin laden himself. I'd like to see the puffer and/or ETD used too. Beyond that, I don't want to see any kind of ID or background checks being used as a condition of free passage throughout the planet.