When is a tripod redundant?
For things like deliberate long exposures, HDRs and panoramas tripods will never be obsolete.
The engineer/geek in me says you can calculate this mathematically...for a given field of view and number of pixels, and assuming some reasonable approximation for the velocity of hand-held motion, you can convert the motion vector to a value in pixels per second; then calculate a shutter speed at which the amount of movement would be less than 1 pixel. If you move less than 1 pixel while the shutter is open, no blurring can occur, so this is the threshold at which a tripod would stop being useful for eliminating movement.
Of course the hard part is figuring out what your hand-held motion velocity is (different for each user, and depends on lots of different factors including technique, fatigue, and coffee consumption). Somebody (not me) would need to experiment to come up with something that would represent a reasonable approximation for most people, then we could do the math and come up with a number. I don't have the time, nor do I care enough to try, but if somebody else wants to, I'd be happy to help with the math.
For the non-geeks in the forum, the 1/focal length rule is probably close enough...
|Blue and yellow in water by fireplace33|
from Ink and water
|Kylmä joki kopio by Kaappo|
from Shutter speed 1/25 or slower
|WR_2.8_13 copy copy by photoprof|