Data does not have to come over 3G - my son is on campus with WiFi everywhere. I live in a community with Wifi everywhere around the city. We both have iPhone 2Gs, which, until recently, were without a data plan.
AT&T has decided that ALL iPhones require a data plan, regardless of whether you paid full retail ($600) or the subsidized 3g/3gs price of $199. It sucks!
I was planning on upgrading to a 3gs, giving my 2g to my other son, but not if I have to pay for a data plan, when WiFi is everywhere here. This is why I bought the 2g, as you could shut off the data plan. I even shut it off on my data plan on the AT&T configuration page of myAccount. Now that option is gone as well.
I had confirmed the ability to shut the data plan off, many times with the AT&T customer support. Now they say that the CS staff was "misinformed".
BULL! If I have to pay for services that I don't want or need, I want the subsidized price. Where do I go to get my $400 per 2g iPhone (the difference between the $600 and the $200 3g/s subsidized price).
The iPhone experience, software, and iTunes ease of use, make the iPhone an unparalleled device, but I am seriously considering leaving AT&T after 9 years, because of this debacle. It is no wonder that people hate AT&T - customer service like this is sickening.