alt Hacker News> use a $200 camera and photograph your keyring from a couple blocks away
Rayleigh criterion: to resolve an angle of 4E-6 rad (key bitting step is 0.015inch =~0.4mm , two blocks is 2 * 200ft =~100m), you'd need a ~140mm aperture lens. Can you really buy one (with a camera no less) for $200?
Well, TIL I'm shitty at the private eye thing, lol. You'd need to get up close, then, or have really good cameras. You're not going to need .4mm precision so long as you can see the differential pattern, though. Memorizing a 5 digit number, each digit between 1-6, and you can remember any kwikset key at a glance, and so on. At most you'd need to print 10 possible solutions if you can't find an absolute difference between lowest and highest points, but most of the time the pattern will have 4-6 potential keys it could be.
Anyway, locks and keys are inconveniences that keep people from casually abusing civil boundaries, is the point, and not all reasons for overcoming those are nefarious.