Shortly after he terrorist bombing in Boston yesterday (04.15.13), the "authorities" (likely DHS) temporarily shut down the cell hone networks as a precaution against other bombs being detonated by remote control through the cellular networks.
While I understand the reasoning behind this action, (perhaps they were disarming the other bomb they (reportedly) found). It did, no doubt, cause a great deal of issues for many urban dwellers who have no other form of communication.
Just a thought: If that is the only telecommunications device your friends and family have in order to contact you, or you the rest of the world, you should have a backup plan.
I'm not talking a way to update your Facebook and such (although you could do that at any shop with Wi-Fi), but a plan to check in with your fellows and family in the event that the Cell networks are down. Perhaps Skype using Wi-Fi....perhaps a number you can call from a land line (if you can access one) to make contact with someone.
Just a thought.