I have a Virgin phone. They buy service and re-sell it. My phone system is different from tracphone in that for $15 every 90 days (with their automated payment system), I get 18-cent-a-minute calls that roll over as long as I pay that fifteen bucks every 90 days. Right now I've got over 80 dollars in calling capacity, so I'll have to start making some calls. :-> I don't have a long distance carrier on my landline and use the Virgin phone for long distance. So far, I'm ahead of the game, but that'll vary on individual use. (I realize there are cheaper long distance services, but the Virgin phone is for emergencies, so I factor that cost into long distance at 18 cents. Long distance is free.)

My wife has a Cingular phone, so we have different carriers. Sometimes I get a signal and she doesn't, so I like having different carriers.

My expectation in my area is an earthquake. I expect landlines and cellphones not to provide a dial tone for a long time after the big one for a number of reasons discussed in this thread. An acquaintance of mine lived in Manhattan during a big power outtage there, and he said people were using cellphones to light their way into darkened building looking for payphones - they still worked even when home phones and cell phones didn't give a dial tone.

Bring your own quarters, and call someone out of town so they have a working phone to answer. I have tried to use a pre-paid card at payphones that won't dial an 800 number because the owner of the phone won't get paid enough. shrug - be prepared with quarters and pre-paid cards. There's no one answer.

Cell carriers like to respond to disasters in a big way and be the first to get their service back up and brag about it, so I suspect cells would come back before landlines if the landlines are destroyed. (COW - cells on wheels.) My expectation, though, is that demand will far exceed dial-tone-ability, so who knows when useable service will reappear.

I think there is no one answer, so having back up systems seems like a good idea. A cellphone from a different carrier, pre-paid cards, quarters, and get a ham radio license. Sit back and contemplate the current status of New Orleans. My expectation is that if we have a huge earthquake in the San Francisco Bay Area, we'll be like New Orleans in terms of recovery.