To your question of an example, though, I imagine you see your fair share of sculptures and statues in Photosynth. They provide an easy example.
If I want to zoom in on a statue's face (if this weren't compelling, why offer zoom?) and rotate through different angles (if this weren't compelling, why offer Spins?), I don't really want to have to zoom out every time that I want to move around or turn the object and thereafter try to zoom back in and get the same framing that I already had.
I zoomed in on a region because it was interesting.
I then want to turn the object because that's what convinced me to load the Spin in the first place.
It just runs completely contrary to the human instinct to examine something to move to a great distance from it every time you turn it over in your hand to see it from another angle.