True. The issue in New Orleans, though, was that the 911 call center was under water - it was uninhabitable, inoperable, and had no outside connectivity, so attempts to transfer operability failed and callers didn't know it. Eventually calls to 911 in NO were routed to Baton Rouge, but no one told Baton Rouge about it, and the onslaught of callers was unexpected.

We've got portable repeaters in one of our ham clubs, but I'm expecting things to go bad for longer than emergency gas and batteries for repeaters will last, if we have an NO-style earthquake. My hope with HF radio is that we can communicate with the outside world, pass some health and welfare traffic, and maybe get some attention when search and rescue people can actually get here.

Most mobile telephone networks operate close to capacity during normal times and large spikes in call volumes caused by widespread emergencies often overload the system just when it is needed the most. Examples reported in the media where this have occurred include the September 11 attacks, the Hawaiian earthquake, the 2003 Northeast blackouts, Hurricane Katrina, and the 2007 Minnesota bridge collapse.
Also, terrestrial cell antennas and networks can be damaged by natural disasters. Satellite telephony can avoid this problem and be critical in natural disaster communications. Satellite phone networks themselves are prone to congestion as satellites and spot beams cover a very large area with relatively few voice channels.

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I expect news services to tie up satellites, too, in a big emergency as they use satellite phones and modems to stream video back to HQ.