I figured it out: it's an internal business unit problem at the phone giant: There must no integration between AT&T's wireline businesses, which sell DSL, phone lines, and Wi-Fi, and the former Cingular as regards Wi-Fi. That would explain the lack of a Wi-Fi data plan alongside the cell data offering for the iPhone.

Cingular always had (and still offers) a crummy Wi-Fi plan compared to two-buck AT&T WiFi (formerly SBC FreedomLink). Prices were much higher and locations fewer. Cingular was 60 percent owned by SBC-cum-AT&T for the longest time, and the AT&T-SBC merger is still in the recent past; their "silos" may still reflect this.

I can't think that AT&T executives simply didn't think about this, but it's possible the integration between the former majority subsidiary wireless carrier and the larger business meant they didn't think about how this could work together. (AT&T's Wi-Fi page notes that it's run by AT&T Internet Services (ATTIS), by the way.)

What it means if you buy an iPhone and are an AT&T DSL customer, is that you should sign up for the $1.99 per month plan so you can use the 10,000 locations in their Wi-Fi network.

Boingo would be an option, too, of course, now offering unlimited access to tens of thousands of US locations for $22 per month and 60,000 locations (soon 100,000 worldwide for $39 per month. While Boingo requires a software package to use its locations, there's almost always an alternate method of entry--more tedious, of course, but a Boingo spokesperson said most hotspot partners let a user choose Boingo and enter their user name and password.

And one of those partners that does that? AT&T, naturally.