Re: Camera phones at sports events
you do have gps, exif, wifi and bluetooth data, being recorded/transmitted on smart phones.
I don't see it as being easy, but possible, imagine I enter a stadium via gate 'f' smart phone in pocket, the time and location could now be known, but even if I was pointing my smart phone in the right direction, it is improbable it will capture anything worthwhile, as reference to my location, via mapping of the stadium shows this. However those that enter through gate 'c' should have a good view, with gate 'a' also possible.
You could also grab facebook and twitter for the event/incident and match up the data.
post mortem, you will certainly have something worthwhile, whether this is a 3d image or not, I can see law enforcement, marketing, sale etc. loving the idea, time to get my tinfoil hat :-)