I do it all the time... but not cause I forget.... My bike is rarely out of eyeshot...

On the rocket... maybe once or twice.

On the chop... never.

gas... with basicly the cost of a budget house... I'd fucking hope not!

What's the proper etiquette if you park next to a stranger's bike and notice a key in it?

Don't steal their bike.

Have them paged at whatever store it's at? Maybe drop the key off at a register/cashier?

I'd leave a note that I gave the key to security... or when people leave their helmets that I placed it in the helmet. (just make sure the note is kinda inconspicuous)

Def done it before.... more often in the rear cowl lock than the ignition.

yeah, i've definately left it in the trunk lock before, but i don't think i've ever left it in the ignition.

back when i had the street rod, you took the key outta the ignition after you started the bike and put it in your pocket. now that took some getting used to, a bike that runs without the key.

my nightster has a flip out license plate on it, that was a dandy stock feature. well, i am embarrassed to say how many times i've ridden it so far and forgotten to flip the plate out first. i'd get to a stop light and think 'oops, forgot the plate'. then i hafta reach back and flip 'er out quick. i'm gonna get pulled over sometime for sure.

I don't think I ever did on accident, but left mine in the ignition in the garage all the time. Since I worked at home at the time, I was never worried about it.