For the sake of argument, how would one keep the Lojack for Laptops from doing its thing, and leading police to a thief? Since the whole setup is actually based on software, wouldn't the following measures:
1) Remove battery as soon as possible
2) Boot from a CD
3) Format the hard disk
4) Install new OS
...Defeat it? Of course, this means you'll lose all the data, but for most thieves this isn't a particular concern.
Because I... want to steal a certain someone's laptop... sssshhhh...
Seriously though, an annoying friend kept on insisting I get the service, and I keep on telling him that if people really want to steal your laptop and get away with it, they will! No anti-theft system is foolproof, especially one that looks majorly dependent on software.
I've heard of a few systems that use on-board chips separated from the disk that can lock things up...but I don't know how you're supposed to defend against the hard disk being taken out. All in all, you're right, there's no good way to protect your stuff other than to not let it out of your sight. That's what I do.