Find My Mac: What is the use of it?

Hi forum,

can anyone tell me a valid use case of Find My Mac?

First off, acccording to http://support.apple.com/kb/TS4006:

"Find My Mac can only locate your Mac if it is connected to an internet via a known Wi-Fi network. If your Mac is connected to the internet only by an ethernet cable, Find My Mac will not be able to locate your Mac."

So the computer needs to have an Internet connection (no surprise here), and even more so, it must be a Wi-Fi that Apple knows about (in order to know its location).

For me Find My Mac would naturally only be really useful for a laptop. However I also fully encrypted the entire harddisk with FileVault 2.

So what happens when I forget my laptop, let's say in a train, in a restaurant, or worse, it gets stolen? At that point it is most likely turned off, and no one except me is able to even boot the system! So no network connection can ever occur (right?), and at this point Find My Mac is totally useless.

Let's assume the person stealing my Mac would then wipe the harddisk (because the current installation is totally useless for him/her) and install a new OS X. Let's even assume that person would even enable iCloud with his/her own Apple ID and even enable Find My Mac.

Would I then be able to Find My Mac? Would my Apple ID somehow be tied to some internal hardware ID of my Mac? Would that hardware ID be transferred somehow to Apple, each time the newly installed OS X would "connect with the Internet"? Or does the OS X regularly send its location (once iCloud and Find My Mac is enabled) to Apple? With or without some hardware ID (which would associate it with my Apple ID, and not just the Apple ID of the thief)?

But what if the thief is not that stupid, and doesn't enable iCloud on his/her newly installed OS X? I mean, it's not like each Apple device reports to Apple automatically (in certain intervals even) when they are connected to the Internt (I hope!) - except off course if Find My Mac is enabled.

So can anyone comfirm that Find My Mac is completely useless in combination with FileVault disk encryption? Or did I miss something here?

Thanks, Oliver