I was in (Dublin) Ireland recently; everyone has broadband, everyone has wireless routers provided to them by their ISP. You seek for an AP on your laptop in a normal neighbourhood, and you'll get dozens of SSIDs. They're all nearly-identical, with the ISP's name embedded in the SSID, and they're all WPA-secured.

I don't understand why North American ISPs don't do the same thing. This would go a long way towards fixing this legal problem. People who don't know what they're doing will just use the router supplied to them by the ISP. Those who want to share their networks will open them up explicitly, and they won't prosecute.

Of course, there'll always be jerks who set up a honeypot and then prosecute you if you "trespass".