And you'll also have to agree who is #8 and #9. One is not without more controversy than the other.
Still, opening it up to teams ranked that low still cheapens the championship, IMO. The top two teams settling it is ALWAYS better than any other pair of teams, every time, without exception.
I don't want to watch a story; I want to crown a champion, and I want it to be the best team, not the one that pulls off the most timely upset.
I don't think it cheapens anything. A team might have one bad game halfway through the season and get knocked out of the BCS top two yet still be the best team in the country. Really, a team coming from #8 to win the championship doesn't cheapen anything. The problem as duke and chris pointed out, is who is decided which are the "top two" teams. The BCS formula and human voting have lots of flaws. Many coaches have admitted they have assistants fill out their ballots for the coaches polls. And a lot of east coast media types never even watch the west coast teams play so they have no idea how good they really are.
Look, those who favor a playoff simply want the whole question decided just like every other NCAA sport: on the field. Until then, it will always be just why I have always called it: the Mythical National Championship. It's like some of those "13" national championships that Alabama claims. Some of them were awarded years later in seasons where they didn't even win their conference or a bowl game, yet Alabama still gladly claims them. And really, nobody can stop them, since nothing was every decided on the playing field.
Oh yeah, I do want stories during stuff like the NCAA basketball tournament. As a fan, I watch those games to be entertained, and those schools often provide great games. The story is just a side event.