Actually, contrary to popular belief, you CAN track a MAC address. Is it something that many hackers are able to do? Yes, thanks to many services available on the market that are completely legal (some of which, I have no idea how). Is it a plausible thing for a typical hacker? Definitely not.
With that said, if you're wondering if organisations can track a MAC address (like the NSA), the answer is YES; and it's being done to this day. The methods are advanced, and rely on many legalities for them to do so, but it's within their means. There are also many ways to track it, like ISP subpoenas, but this is something that goes to a whole different level.
Bottom line: yes, you can track/trace a MAC address over the internet, but to a certain extent, depending on who you are, and what methods you use.
Actually, I was half right, half wrong... If someone is using the same ISP as you, they actually can trace you. MAC addresses are broadcast through the network (aka the network that all computers connected to the ISP are on), therefore someone could, theoretically, trace your computer. That is, if someone is inclined to do so. And yes, this can be done by some basement hacker with a little know-how.
I ran this by a buddy who actually has done a lot of IT work, and he corrected me on that bit.
Update: One example of how a MAC address can be traced is by sniffing traffic on a major network. For example, if you're a COX customer, and you set up your router right, you can watch all the MAC address traffic on the entire COX network. Don't believe me? Talk to COX themselves. The way the network is written, the MAC address is publicly broadcast over the network (aka your connection to your ISP, which then connects you to the internet), mostly because it makes life so much easier for the IT guys. Also, there's really no sense in hiding every user's MAC address when they actually have a use for it (ie: law breaking customers).
Now, if you mean using it to find the exact location of a person, that's a jumbled bag of yes/no answers. But, I still stand with a basic fact: YES, you CAN TRACE A MAC ADDRESS. Prove me wrong, that's all I ask.