How Time Machine could work with portable machines

I've been thinking about how Apple could implement Time Machine, their auto-backup tool, for laptops, or machines without enormous data stores inside. Given their sucky network hard-drive implementation on the Airports of late, will they go that route? Probably not recommended, but maybe. Lord I hope Finder doesn't wig out everytime TM tries to upload 122k of incremental Word changes. Ouch. Can I have my OS 9 back?

Anyway, wired drives will be the way to go for safety's sake. Now when you undock, and happen to be unplugged from your drive, what happens? My hope is you can tune a little portion of your local hd to serve as a temporary storage facility. Secure? Not really. If your hd craps out totally you're screwed. But if you kernel panic or something it'd work like magic to restore all those "unsaved" changes. But Apple, give us a chance to set the limit, OK? You gobble enough resources as it is.