Geotags, aerial synths, street synths… capturing events as they happen. If you can mark it on a map, then this is the place to talk about it.
Could Photosynth be used to combine old photos and make synths of towns, so you could see how they where in the past?
If you had enough photos, there is no reason why you couldn't, but it is unlikely that enough photos were taken in the old days.
I recently tried making a synth with historical photos of St. Louis. Didn't work at all. I think it was because they were black and white. Only tried once though.