Seriously, there's absolutely no point in getting a BlackBerry or an iPhone without a data plan. It'd be like buying a Ferrari and only ever using it to pick up groceries. And yes, the data plans on BlackBerry's and iPhones ARE mandatory. At least on AT&T and Sprint.
I'm pretty sure you can't even get one without a data plan. It's a "must add" to the phone when you set it up.