It made sense for the Yankees back when they had Wetteland for the 9th and Rivera going two innings in front of him; you had to beat them in six innings or you weren't going to beat them. I don't think shortening the game by one inning is worth earmarking the best arm in your bullpen solely for one-inning save appearances.
A closer is good for what, 70 appearances max? It seems a criminal waste of resources to have half of those appearances come in two- and three-run games that you could just as easily close out with Johnny Nimrod.
Of course it makes sense, but not every team has two shut down relievers like that.
Sure, you could run out any reliever with a 2-3 run lead, but they wouldn't be very consistent. That's the biggest difference between elite closers and other bullpen arms, they are lot more consistent. You can count on them to get three outs no matter who they face and they have the confidence they can do it. Other guys, you use in match-up situations because they can't get a lefty out, or they struggle against righties. But closers should have the ability to get anyone out, and that's what you need at the end of the game.
That's why closer by committee doesn't work very well, just go look a few years ago when Atlanta tried it. And in 2003 when Boston tried, but eventually gave up and turned to BHK.
Here's a very good article about bullpen and closers by committee, with lots of good quotes from scouts, managers, front office guys, and Pedro Martinez.
Well, Martinez said again that he was concerned about a 40-save man slipping away. "When you have a guy who saved 40 games for you, it's difficult for you to understand that you're going to really just hand the ball to a committee of relievers that you have never seen before," he said after Monday's game. "To me, it's the first time I've ever seen this happen. Maybe for Grady it's not. But for me it's something new. I am going to have to trust Grady on that and just shut my mouth and continue to do my work.
And you look at
this article stating that the Twins will go with a closer by committee this year. However, that didn't last long, as Jon Rauch eventually took over the closer's role. And now it's Matt Capps' job since they traded for him.
Lot's of teams have tried your idea of bull pen by committee, but it just doesn't work as well. There are always going to be blown saves and leads given up by bullpens, that's baseball. Changing around your bullpen isn't going to change that.