I was starting a "We're watching you!" response but thought better of it.
If someone wants to really track you, it would be easy. You got a cell phone? Turn it on and once it connects to the network you can be found. You use credit cards? You can be tracked. You live in an urban or suburban area in the US? You're under almost constant surveillance commrade. Da. 1984 made manifest. You drive and use EZ Pass through toll booths? Bingo. Depending on where you are, they even know your average speed. You use store discount or club cards? They know what you buy, what you eat, what you read. You use your MacBook at all? It takes little time and effort to remove your hard drive, make an image of it, return it, and leave no trace of having done so. I could go on, but I think you get the idea.
That said, I'll present the other side.
I'll guess that to the government, you're boring. You're of no interest to them. You're just an everyday dude or chick who does normal boring things while sitting at your Mac. ("Hey, let's look at this guy staring at his screen! Wow, this is exciting.") Maybe you're handsome or pretty or cute or homely or ugly. Maybe you have this great laugh, maybe you laugh funny. Maybe you pick your teeth or, God forbid, well I won't go there. You're nothing to them and would be more boring to watch than Justin TV.
I don't doubt for a moment you could be surreptitiously monitored through your Mac. Technically it could be done pretty easily, and without the LED being lit. Why though? What would be the point? It would reveal nothing to law enforcement, and to do so legally would require a court order and then for specific monitoring activities for a limited amount of time. There are lots of better and more effective ways to monitor you.
"We'd like a court order to monitor mathogre while he's at his MacBook."
"Hmmm. Why?"
"We think he's wearing cute jammies tonight."
"Okay, sure. Go ahead. Here it is."
I think the MacBook is pretty safe, even with the built-in camera and microphone.
