In urban areas, yes, I would say without reservation if you're running 802.11b, even with WEP enabled, and you have a DSL or other broadband connection to the 'net, you are at risk. You'll have your AP detected, cracked and cataloged before you know it. Then your risk is of either data theft, or having your system used for a spambot or similar use. As you say, you might get shut down by your ISP, but the real risk, IMO, is that you would get a rootkit put onto your systems that you'd not notice for quite some time.

In rural areas, off the beaten path, the risk is nowhere near as great. There just isn't the density of open AP's that would attract hackers, and people driving around with antennas pointed at people's homes will be noticed.

Here, where I have a clear field of vision all the way 'round, there is no way someone could escape my notice of their trying to latch onto our AP, so while I have WEP enabled, I know there are risks and we don't have the Windows file sharing enabled on certain machines, but I'm not using LEAP or password/SSID rings.

Some outside hacker wandering into this valley, snooping into people's business has a lot more to worry about here than in urban areas where they might get picked up by the local LEO's or FBI. Sittin' on your front porch, strummin' on a banjo tends to keep most of these pencil-neck clowns pretty scared off, if you get my drift. ;-)