The problem with any form of wide-area wireless communications, whether based on cellular technologies, WiMAX, or public-access Wi-Fi, is that some infrastructure is required. Disaster recovery is a major challenge, and emergency response agencies often have the ability to get some form of wireless on the air quickly. Similarly, cellular operators have trailers called "cows" (cellular on wheels) to get at least part of their network back up quickly. But since there's no guarantee that any particular network will be up at any particular time following a disaster, the best strategy is to have mobile devices and accounts on multiple services. That's what I do -- I carry two cellular and one Wi-Fi device at all times. You can equip notebooks with cellular-based connectivity in many cases as well. Good luck!
This was first published in January 2007