I bring my cellphone when I go riding too, its just incase something were to happen to me so I could contact someone. So far I have been lucky and haven't had to use it yet. There are some people there who call their friends and such while they're riding, but I'd find that distracting.

My sister was at a friend's house and the girl didn't feel like getting up and going to ask one of her parents something, so she called them from her room on her cellphone. It's pretty sad how lazy some people can be! (Her parents where just one floor below her)