[dnanian]

Well -- not so sure 'evil' is the right term. Necessary good, perhaps?

But, anyway. If you partition the drive into three appropriately sized volumes, using the "GUID" partiitoning scheme and the "Mac OS Extended (Journaled)" format, yes, you can take it around and back up each Mac to its corresponding volume on the one big drive.

I think it's better to get a separate drive for each, because it won't be as much of a hassle, which means you'll actually do it.

It's always better to have a FireWire drive if you can. Using a Time Capsule is fine as a secondary backup (or for Time Machine).