We just had this conversation in our home recently. My daughter is 11 and in the 5th grade. I guess you could say we made a list as to why or why not. We ultimately decided not to get the phone just yet and surprisingly our daughter agreed with the reason why not to have one. Here is the main reason we chose not to.
1. We asked her why she "needed" a phone not why she "wanted" a phone and the answer was to listen to music and play games and text her friends.
No phone needed. She already has an ipod. She was not upset and later said your right mom (love hearing that) I don't really like talking on the phone anyway, it's just everybody else is getting phones.
Ultimately, it comes down to knowing your child and the needs of your family. We have decided to revisit this conversation as she gets more and more involved in school and sports where it might come in handy to have her able to give us an update.