If I was in an emergency, I would definitely call 911 (if in Sacramento - though I wonder). I would save my precious minutes on my cell phone making urgent calls than logging on to Facebook and updating my status. Though, on the other side of the coin, look at what happened in Iran. It was the Twitter updates that help post other countries what was going on.
But it was more for reporting rather than asking for immediate help.

What is funny is this reminded me of something that happened with my daughter a few months ago. We were watching TV and there was an iPhone commercial and in it the announcer said, "Lost, there's an app for that' and they showed the iPhone with a compass app. My 12 year old daughter turned to me and said, "if you are lost and you have an iPhone why wouldn't you call for help?"

I laughed until I realized that there are some people out there who are so into their gadgets (which I consider Facebook and Twitter to be gadgets) that they totally miss the obvious solution.

That is interesting, I think you may find this interesting though. I go out to the desert frequently. Well I've experienced that sometimes I can't send out a phone call but I can send out texts and sometimes get on the net. I think that being able to text for help to a service like 911 would be really useful for people who end up in areas where all they can send is a text. I'm not sure why texts and internet work when phone calls won't. I am not saying that you should post on your Facebook if your in an emergency you should most definitely call for help but I can also see where you can only send out a text or get to Facebook.