I really wouldn't get too down on yourselves about Harvard. If a majority of people knew what the "magic combination" that Harvard was looking for, well... it wouldn't be Harvard. Now if this was law school or business school... I'd be singing a different tune.
I don't envy the Harvard admissions committee at all... from a sheer statistical standpoint, their job is daunting. Just imagine the number of applicants they have to turn away that have not only outstanding numbers (like shoombol... great stats btw), but also with extensive extracurriculars and research experience. Let's face it... the people who are applying to Harvard (with the few exceptions of some applicants that are EXTREMELY hopeful, maybe borderline delusional, about their chances at the "H" bomb) are all gunners in one way or another. To make things worse, with a class size of only a mere 35 people, they have to look outside the box for those X factors (i.e. "extraordinary life experiences" - whether it be an advanced degree like a PhD, extreme adversity faced during life, exceptional instances of community service, and maybe even ethnicity), as someone previously mentioned, otherwise their job of selecting their class would be impossible.
Shoombol is right - look at the Harvard interviewee stats on predents. All of them have impressive GPAs, but when it comes to DAT scores, they're not jaw-dropping by any means. So, just because you've been rejected from Harvard despite having great numbers and a great application doesn't necessarily mean that you're an "undesirable" DS applicant. It might just mean that you don't fit the Harvard "mold" - some people are fortunate enough to fit that mold, some can only dream of it, and others have no desire to.