Many road races either discourage or ban the use of headphones in the entire race or at the start or finish.
The reason is simple - when you are in a race you must be aware of your surroundings and be cognizant of instructions from race officials and course marshals. In most races roads are either closed or traffic controlled but there are always instances for example where a rogue vehicle some how gets on the course. A race official will warn the runner of a potential safety hazard.
But the use of cell phones and proliferation of them with running apps has taken things to a whole new level. You can see runners at the start or finish or at strategic scenic parts of an event these days taking a "selfie'.
This can be especially hazardous with runners behind running into the "selfie"" runner.
So, should races ban "selfies"? Have you ever taken a "selfie" during a race?