Apple sells a lot more WiFi iPads than it does 3G iPads. Best data I could find on a quick google is admittedly almsot a year old, but:

90% of the tablets use WiFi only (some have inactivated cellular chipset) meaning that only 10% of the tablets (as of Q4 2011) were cellular activated. Operators who start to bundle multiple devices by single data plans and data buckets are going to see a better yield in this category. We expect family data plans to be introduced in the US market soon.

Source: http://www.chetansharma.com/USmarketupdate2011.htm

I don't mind this so much presuming it can do Bluetooth tethering with my phone [vs WiFi due to power usage issues]. If I'm the device's user, I'll likely have my phone with me, so having a redundant radio in the device doesn't add value. And, if I let someone else use the device while I'm not around, the likelihood is that there will be an available WiFi source.

I'd like it-just-works connectivity between my phone and any other devices I carry with me. Right now, I have to hit a couple buttons on both devices -- a pain for short-term usage scenarios.

I can get tethering to work, my mom: never. My parents both got iPads and a device that isn't just online all the time could never ever work for them. iPad really set the bar on that one.

Yeah. Tethering still is too mysterious. If it's not working, which device is at fault? For awhile (pre-ICS), my Droid RAZR had a bug where it required a reboot before the hotspot would work. Of course, it failed silently and claimed to be making itself available!

The thing about it-just-works connectivity is that it will generally halve battery life on a smartphone. You basically have to keep the radios constantly on and scanning for known connections.

I know little about Bluetooth 4 except that it's supposed to be low power. Could it be used to "scan" for interested/allowed devices and then "step-up" to a higher power, higher bandwidth connection?