I think that's because the ACC has a contract with the BCS, and the champion is guaranteed a spot in one of the BCS bowl games. It was like that before the BCS ever started. What game is it? I think the ACC winner always used to go to the Cotton Bowl or the Orange Bowl. That's why they get to go, because the ACC allways sent their champ to that bowl. I think all the BCS did was make it so that it wasn't allways the same bowl or something. Also, if the ACC champ goes to the national title game, the BCS picks an at-large team from the BCS standings to go in the ACC's spot. Other than that, I think it's the same way it's allways been. It's just like the Rose Bowl was and is. It has allways been the Big Ten champ vs. the Pac Ten champ. The only time it isn't is every 4 years, when it's the Rose Bowl's turn to host the national championship game, in which case the 2 conference champs are given spots in one of the other BCS bowls.
P.S. I think it's pretty lame that a team with 5 losses won the ACC. :napplause