I didn't know 802.11 was a viable broadband Internet solution, I assumed it was just for company LANs and campus area networks.

All it requires to go long-distance is a directional antenna hooked into a jack on the 802.11 transceiver.

My ISP has built his own custom routers from off-the-shelf parts. They're tiny little PC's on a board with some flash RAM, ethernet, and PCMCIA sockets for the tranceiver cards. He's written his own routing software to run from the flash on these things, he puts in all sorts of great little features. They're firewalls with DHCP and NAT and everything.

Give you one guess as to which Linux distro he uses to write the embedded code on these things. Yup, Debian. His routers are like tiny little Empegs, I'm not kidding.

Aren't there security concerns?

Yes, but only to a slight degree. There are things which help us out, though:

1) He locks down the routers so that they will only accept transmissions from specific MAC addresses. So my router will only talk to the next router in the signal chain.

2) The antennas are directional, so you would have to be within the narrow range of the antenna sweep to hijack the signal. Or you would have to be very close to the router to get the omni signal.

3) The router itself is locked down pretty tight, so even if someone managed to spoof a MAC address, they would basically be in a situation that was no different from someone on the internet trying to packet-sniff transmissions outside a firewall.

My internet transmissions aren't top-secret, though, so it's no big deal to me even if someone does packet-sniff my stuff. And I don't leave my PC's on all the time, and they're behind this router/firewall, so I'm not worried about hacking much.