It would be invaluable in determining cause. Terrorist attacks, crime... Good point, but it would also obliterate privacy. I read a story once, might have been Bradbury. There was a machine that supposedly let you view the past. You could dial up, say Congress on July 4, 1776 and see what happened.
But it turns out that you could also dial up your neighbor's bedroom three picoseconds ago.
SD
"But it turns out that you could also dial up your neighbor's bedroom three picoseconds ago."
Forget time travel on that one, we might be headed that way in real time. Ever looked into "panopticism?" Not the Foucalt mumbo-jumbo, but ultra-lowcost, embedded surveillance.