For those of you who haven't used FON, a quick primer: you probably own a wireless router at home. If you travel, you may end up searching for Wi-Fi hotspots in cafes, hotels, et cetera. For those of you in the U.S., this is no big deal. But FON is a Spanish startup, and for those that travel in Europe, purchasing a T-Mobile or France Telecom or other Wi-Fi subscription is expensive.

With FON, you agree to purchase a FON-branded router (La Fonera) for $39.95 (or about $28 for a PC card) , leave it on 24/7, and dedicate a small portion of your Internet bandwidth to public surfers, who are barricaded from your system via a firewall. In return, you can surf for free on other FON routers. The agreement allows Boingo users to roam onto FON hotspots.

Now here's where it gets interesting.

Most users are what the company calls "Linuses", or normal users, who leave their Fonera on at home and roam for free. "Aliens" turn their Fonera off, and are thus charged $3 or 3 euros per day to roam on other FON routers.

"Bills," however, don't get free roaming. But they do get to charge others for the use of their Fonera hotspot, and they get 50 percent of the take. So if you live out in a subdivision, chances are that you'd never see a dime. But if you've been to Europe, imagine owning a Fonera within range of a train station. Or placing one near a cafe. Not bad, eh? Also, there's nothing prohibiting the purchase of multiple Foneras, and setting them all up as "Bills".

I wonder if anyone has purchased two routers, set one up for billing, and the other for free, and then "accidentally" placed the free router under a tinfoil pyramid. I've seen some other people suggest that "Linuses" get credited with a day pass for free roaming based on a certain of uptime on their own Fonera. So far, however, FON hasn't bitten.