I need to introduce a new concept into Wi-Fi access: not backhaul, but backside utility: That is, how useful is a Wi-Fi location if you can't sit down comfortably and without risk of expulsion? (An alternative construction might be an "assiness index," but that's too offensive for regular use.)

My essential problem with Fon is that there's no good way to determine how many of what they describe as nearly 200,000 Fonero locations are really hotspots rather than an antenna sticking out of a house or some inconvenient location. To me, a hotspot is a spot with high backside utility. If I can't sit down, potentially get electrical usage, but at least sling my bag somewhere, I can't work productively for long.

Making a phone call requires little backside utility. You can stand and walk around the pavement to make a call, often in inclement weather, as long as ambient noise isn't too high. But at 11 pm in a residential neighborhood, you're unlikely to make that phone call--or the police might be called.

In speaking recently to the BusinessWeek editor who wrote up the Fon/BT deal, I tried to explain how I debate Fon's count of 200,000 locations as comparable to 200,000 hotspots, because Fon doesn't have airports, convention centers, downtown hotzones, parks, or metro-scale networks. All of those vary among their backside utility, the captive-user potential, and the public-access-without-harassment possibility. But they're all large. Access across 1m sq ft of an airport isn't comparable to a sliver of use on a street in Barcelona outside someone's apartment.

Thus I was remiss in my discussion of the BT deal in mentioning that Fon could be a key improvement in BT's converged calling (unlicensed mobile access or UMA) service called Fusion. BT spun off its cell side, so in order to make Fusion work, they need as many minutes spent at home or at OpenZone hotspots to keep from burning up GSM minutes. If a good hunk of BT's wired DSL customers flip the Fon switch, then there is, in fact, a high probability that a Fusion user would see a dramatic improvement in how few minutes were fried via GSM. This reduces BT's cost and improves a Fusion subscriber's monthly bill, too, if they would otherwise have gone over their minutes' pool. They would likely see better coverage in areas with poor cell service, too.

So while I want to emphasize that backside utility and public use without harassment are two factors in how you might say whether a location is a hotspot or just lukewarm, applications are a critical component. If I need to look up a fact on my smartphone, and I can use Wi-Fi to do so via a Fonero's network, that's very high utility and I don't need to sit down or linger. If I want to spend 60 minutes reading email on a laptop, I need a seat.