[citation][nom]jellico[/nom]You should always be careful when accessing "free" wi-fi networks anyway. Hacker will sit in airports and bus stations and configure their laptops to be ad-hoc wireless APs. You can, in fact, access the internet from those connections, but they are capturing all of the packets for analysis and attempting to access your computer at the same time.[/citation]
I had this same thought driving into work this morning (not sure why, musta seen Wi-Fi on some billboard or something).
If a store says it offers "Free Wi-Fi", make sure you know what the name of their network is. I know I've seen multiple available networks in various airports and hotels before. Oh, and if you're using XP, upgrade the damn service packs!