I won't take an actual stand against cell phones, because I think there is a place for them, such as when the camp is many weeks long or when a child is young or fragile for some reason (medically, or just sustained a loss etc).
But I can tell you that it can become very hard for a child to become immersed in the full camp experience if they can call out or get a call in at any moment. A faculty friend of mine who has been leading college trips for decades says that it seems much harder for college students to separate from their friends and family these days. They call home to report every small happiness or disappointment. Small interpersonal problems that could have been solved pretty easily escalate rapidly when everyone calls home to tell friends and family their side of the story. And they miss a lot of the trip because they are thinking about home and talking to people at home and not taking advantage of where they are.
Not giving your child a cell phone at camp, I think, can send the message that you really have confidence in them, that you think they have what it takes to get by without you, and that you are able to let them grow up and be independent and even make mistakes and figure out how to fix them on their own. So DS has spent a total of 2 weeks at camp with no cell phone and has done great without one. It's been harder on me, but I am trying to grow up too!
