Rules are not selectively enforced- we ask all runners to follow all rules all the time, but trust people to use their judgment. Remember, staff is limited and many are volunteers. USATF made the no headphone rule mandatory last year, so all race directors with USATF sanctioned races should be enforcing it. Also, there have been several incidents recently, such as last week when a UNC University student running wearing her IPOD turned into the path of a bus on a campus road.
http://running.about.com/od/mentalaspects/f/runwithmusic.htm
If people want to wear headphones whilst running, they can- just not in USATF races. If it causes 10 people to choose another race so be it. It is a small price to pay for the safety and peace of mind for all runners. It really brings it home when you read of a young woman with everything to live for having her life cut short. I hope runners will understand that volunteers take on a huge amount of responsibility when they agree to put on a race- we need the support of everyone. Oh, Twin Cities Marathon in the fall went through finish line photos and DQ'd those wearing headphones. Imagine running 26.2 miles and NOT having your time recorded!