Playing a remote DVD

Remote Disk is designed for the MBA to install program, so can only share CD/DVD-ROM computer disks, not movie disks. AFAIK, there is no setting to make work for movies. (We have to be careful with how much assumptions we make when listening to the "sales pitch." 😉 I watched the keynote for the MBA and I don't remember it specifically mentioning watching movies remotely. If someone knows otherwise, please chime in.)

Short answer; you need to view streaming movies (e.g.: Netflix) or get the movie as a file stored on the MBA's hard drive. (e.g.: iTunes.)

Some DVDs also come with a "digital copy" which is a file than can be loaded on devices without a DVD drive, which is exactly the situation you're in. Otherwise, to convert the movie to a file usually means breaking the copy protection, which is usually a violation of the DMCA, so can't be discussed here. (Google is your friend.)

The other alternative is to change your broadband device. If you get some sort of "Mi-Fi" device, the MBA connects to the broadband device using the built-in Wi-Fi. Then the USB port is free for the MBA's Superdrive. Verizon, Sprint and others have Mi-Fi devices so you may be able to transfer your account to the new device without changing data plans.

'wonder if a simple USB hub might be a good idea, too - to allow more devices to be connected to the 'Air - assuming it could cope with DVD drive & 3G-stick & whatever, all at once ... ?

The 3G stick would probably be ok. But I've read people saying that the Apple Superdrive doesn't work well with a hub. I think it uses more power than most hubs can supply so is often unreliable unless directly connected to the Mac.

If you can find a non-Apple DVD drive, then maybe you can use that through a hub, especially if the drive is self-powered rather than bus powered. (i.e.: The DVD drive has it's own power adapter.) I've used non-Apple DVD drives on my Mac and they work, but I'm told sometimes the Mac can't boot from them (so you can't reinstall OSX with a non-Apple drive) and I've never tried them on a MBA. But something to consider, particularly if you can borrow one from a friend or try it out in the store, etc.