Good, I hope Amazon knocks Apple off their high horse.

No, iPads are sold unlocked. Any carrier with 3G can sell you a SIM to pop into one, with data plans starting around $15-$20 for 250-500MB.

AT&T does have a neat trick built into iOS where it's super easy to just buy a month's worth of data, then cancel before you're billed for another month if you don't need it anymore, all right from the device. I don't think other carriers can take advantage of that feature (except AT&T partners like Rogers up here in Canada).

Independance from the carriers is one of the key reasons why Motorola and Samsung are having a hard time competing with the iPad. Apple has an easy time getting retail distribution without carriers, while other manufacturers have to bundle their devices with a carrier contract to get their devices out on carrier shelves. 

As far as I know, Facetime is still wifi only, so your carrier will have nothing to do with that at all. And sure, you can use Skype and other audio/video communications apps over wifi or over a 3G data connection if you have a data contract. The iPad doesn't technically make regular cell phone calls, though, just VoIP calls.

And to comment further on the thread, I've kinda given up on Amazon numbers. This is the most information they've ever given, and still for all we know the Fire might not have even sold a million units in December. All we really know about Kindle sales is that Amazon seems pleased and is pushing the platform as hard as it can. Comparing it with competing devices is just impossible to do with data this inaccurate.

As for the iPad, I do think we'll see iPad 2's for $400 in ~3 months. I think the rumours of a super high res iPad 3 are plausible (rumours of a 7 inch iPad are bullshit), and since screen supplies have been the biggest limiting factor in iPad production, I think Apple will want to keep making iPads with the 1024 x 768 display, otherwise it will be really hard to keep up with the growth in demand.

I can't haz Apple is d0om3d option?