Now I never heard this, but this is very possible. MAC addresses are can tell you the manufacturer and then the specific product number. As for him personally, my guess is his ISP was broadband and spilled the information to the FBI, as is the ISP was broadband, they would have to know his MAC address if he connected to their network. So, the manufacturer might have been based close to where the creator was, or they remembered where they shipped some of their parts. And the ISP was probably broadband so they would have to know his MAC address when he connected to their network. Am I making sense? I think I mixed things up a bit.
Somewhere else on antionline I read that the creator of the melissa virus was busted because he created the code with microsoft word, and word secretly appeneded his mac address to the file. Now, I'm wondering exactly how the fbi was able to track him, or know it was him, by knowing his mac address...?