This is serious twitter.

As much as people deride Twitter for being used to convey insipid details of one's daily life, it can actually be very useful.

You can get Twitter updates of emergency announcements for the San Diego fires.
http://maps.google.com/maps/ms?msa=0&msid=114250687465160386813.00043d08ac31fe3357571
The serious use of the custom Google map is also impressive.