>If someone leaves their journal lying in a coffee shop
Not even remotely near the same thing. Can we agree to stop making crappy physical analogies, please?
> If my neighbor leaves their Wi-Fi open, I won't hack it.
It's not "hacking" (or even a little bit unethical) to associate to an open AP - it amounts to an advertisement of a free service available. Really you're not crossing any creeper lines there unless you start rifling through the other computers connected to that AP.