That is the new post on Glenn Reynolds's semi-blog at MSNBC. He makes the point about how, in addition to providing near immediate video of an incident, video cell phones could be of use to first response personnel. The idea is that more eyes equals more information as opposed to the now relatively limited number of security cameras available on the streets.
I would add that such video would be very useful to later responders to incidents, namely investigators. While it would be highly unlikely that the incident itself would be caught on film (not to mention being a cause to suspect the person who shot the footage), information on the immediate aftermath would be very useful in compiling the complete scene. What is the reaction of the people and inanimate elements of the scene? Is there a blast wave evident from that one location? Are the lights on or off at the time of the footage? I don't think that you would need to be Gil Grissom to be able to use that type of information.