Here's my point of view. I agree that the most talented early 20s kids have plenty to contribute and plenty to gain from business school. However I believe that most kids do not fall into this category.
I was certainly not a credible b-school candidate when I was 24. This is partly because I had too much undergrad debt but mainly because I would have had nothing to contribute. I was naive, inexperienced, unprofessional and lacking leadership exposure. I suppose this is a confession of mediocrity, albeit one which I suspect applies to most young people, including the talented ones. There was nothing I could have done to change that in those early years because I was not mature enough to want to nor skilled enough to be able to.
Yet at 28 I believe I am an excellent b-school candidate and can't wait to get involved. I wish I'd been in this position at 24 but I wasn't, so all I can do is make the most of it now. There are plenty of young movers and shakers who got to where I am a lot faster, and full credit to them - I look forward to working with them and learning from them. But I think they are too few and far between to fill all of the top business school classes so focusing on the 24-28 age group will open the doors to more kids who aren't ready. Soo let's not write off the 28-33 guys because they were slower out of the blocks because there's plenty of talent and plenty of potential there still.
What's more, raw talent is not a subsitute for experience, despite what the girl with the subway avatar said in her otherwise excellent post. Her implication was that all the benefits of pre-mba experience can be gained in two years and the rest is superfluous. But after 5 years in industry, I have a perspective that no young rock star can offer. So if you take away all the 28 year old dinosaurs like me, you take away an integral learning opportunity for the whippersnappers who remain.
Bottom line - find the right balance.
If I said something intelligent, it was probably by accident. But click "kudos" anyway - it will make me happy.