Great question. From a safety perspective, I think that they are useful and perhaps even necessary. That said, I think they have contributed to some societal ills as well. My biggest observation is the loss of personal boundaries. Too often I've overheard relationship arguments, discussions about sex, and other things that used to be considered an intimate conversation. Texting in meetings and classes is something that I've also experienced. I've even heard people answer their cell phone in the bathroom while audibly relieving themselves. When did that become o.k.?
Beyond the loss of boundaries, we are creating a generation that is very technologically skilled at using the communication tools, while at the same time losing direct interpersonal skills. The texting feature is contributing to a loss in writing skills in my observation as well. I'm not against the technology, but I think we need to put it in perspective. If I had children they might have a cell phone, but it would be restricted to calling their parents, their grandparents and 911. Period.