AT&T has been teasing us with free iPhone wifi. First it was on then it was off, and AT&T didn't seem to be saying anything. Well the New York Times finally got somebody to say something official and apparently the launch of the service was "human error" but AT&T "has long planned to offer free Wi-Fi to customers with iPhones and other phones that have Wi-Fi capability" as a "way of differentiating the AT&T network and giving customers another reason to choose us over a competitor."
The upshot: free iPhone (and other smartphone) wifi is coming from AT&T, but they're not saying when. My guess is that they may roll it out to coincide with the launch of the 3G iPhone.