I've heard of it but it happens pretty rarely and never to anyone I've known personally in all the years they've been pretty popular. I don't keep my phone attached to me all the time nor do I use it all the time, so I'm not concerned about the cancer link. It would be different if my ear were to the phone all the time. I'm not sure what risk there is from having the phone in one's pocket all the time over the longterm (as in, I don't know if the risk applies just when one is using the phone or if the risk if present just by the phone being 'on' and near the body).