Sure. But should something like this happen, I'd prefer to not waste time having to sit through a complete reinstall before I can start damage control by changing passwords online, etc.
I don't think getting hold of the iCloud password would let anyone "own" my mac. (The only things they should be able to do with that would be messing with my synced address book, notes and photostream - and if "find my mac" was enabled, perform a remote wipe).
Use FileVault 2 and remote wipe is no longer necessary.
On current Macs, a live USB stick might be a better idea than a live CD. Or even better a bootable backup created with Carbon Copy Cloner (CCC) or SuperDuper.
Think of the trade off: what's the likelihood that you won't be able to find a computer...ANY computer...to login to your accounts...versus the likelihood that someone can compromise the stolen computer's entire HD?
(this is less of an issue if you're encrypting everything)
