The number of times I get stopped and asked if I'm okay when I'm, e.g. halfway across a street, halfway down a flight of stairs, etc... I feel like turning to these people and asking how they think I got out of the house and this far into my day on my own, only to suddenly become entirely reliant on them.

Not to mention that halfway across a street or down some stairs (neither of which is an exaggeration, both have happened to me) is a really bad time to interrupt or startle a white cane user who's probably concentrating on a lot more things than you are at that moment.