<a href="http://www.eweek.com/article2/0,3959,1086833,00.asp?kc=EWRSS02129TX1K0000531">Unlicensed Wireless: License to Attack?</a>

I’d go a little farther on this one, it’s not just unlicensed wireless that’s vulnerable, it’s any WLAN that isn’t using strong authentication, ACLs, and encyption to protect the data in transit.