Your microwave doesn't need to be backed up or software updated on a regular basis. Syncing data between the iPad and a computer (photos, books, music, etc) is optional at this point. In the future I assume backups/software updates will not require a computer either but it is a challenge to backup 16/32/64GB to the cloud on a regular basis for most people with mediocre broadband connections and basically impossible over 3G due to data caps/throttling. I guess if we want to stick with the microwave analogy we could say the microwave cannot be activated before being plugged into an electrical socket. It's a practical consideration. We could have microwaves that ran on batteries but what's the point? If you own a microwave you probably have a spot to plug it in. If you own an iPad you probably have a computer of some kind. Worse case Apple will activate it for you.

For the larger issue of DRM I must say I've never used a microwave that was more open than an iPad. I can't load any third party software into my microwave. I can't even find any schematics for the internal designs to allow for my own modifications. I'm pretty sure companies like GE own patents for many of the components inside so I couldn't reproduce them and sell my own open source microwave.