Firmware password protection1 is nice, but would the Genius Bar actually mind my "lost" status noted online if my computer ends up in a store to reset the firmware password (which is the easiest method to reset it)? Do they match the serial this way?
I doubt it, and even if they did, you should not rely on it.
I assume you are concerned about the case where your laptop gets stolen; you want to protect your data. In that regard, the firmware password is utterly useless, the thief could just pull the drive out and access your data anyway.
I suggest you look into something like FileVault 2 instead.