Hey, I was wondering what kind of trouble someone could get into if they were able to hack several E-mail accounts and then use them to send E-mails and IM's to a whole bunch of people just to piss them off
And if an unsecured wireless connection at Starbuck's coffee was used, how could they find you?
HYPOTHETICAL WORST CASE SCENARIO:
Any email that you write will have headers, including fun things like your IP address, host, yadda yadda yadda. Should someone connect that IP to Starbucks, the company could check the routers logs and find the MAC address assigned to said IP address at the given time. If said MAC address is for something like your internal WLAN card or something like that, and you have your computer registered (with your actual info) with the manufacturer, it could come back to you.
Accessing someone else's email address, especially by means of password cracking/brute force, is illegal (duh). I don't know the actual charge, but you could be charged for every account you access, or every message you send. If your email campaign has negative effects, you may also be guilty of harassment (multiple charges).
REALISTIC SCENARIO:
The average Starbucks employee probably doesn't know how to check their router logs, or even log into their router. Your best bet, however, would be doing this from a public access machine (such as the ones they have in Subway), and to not do anything else that would reveal your identity (log into your own email account, etc, etc). MAC Address spoofing would yield similar results.
IS IT WORTH IT?
Depends how much fun you're planning to have. I mean, people got away with hacking Paris Hilton, Sarah Palin, and many other public figures. As far as I know, they never got busted. Just don't associate your name with it.