Reservation for backword classes and why I support the idea

This question is haunting me ever since Arjun Singh announced the increased reservation for the OBCs which took the percentage of the reserved position in all government institutions to 50% approx. I saw many debates regarding this and now I have some opinion on this.
There are two aspects of this issue. One is the about the idea or the concept of reservation itself. Should there be any reservation at all or should there be not? If the answer to this question is affirmative then the second question comes into picture that is how should it be implemented?
Initially I was against the very idea of reservation, especially during my 10th and 12th standards. But, now as I think of it, that opposition was because of me being denied an opportunity of studying in a good institute and not because I thought one can not and should not compromise on quality, which I claimed to be my basis for the opposition to this concept. Now I support the idea of reservation.
Let me explain. When I used to say that students should be given the admissions on basis of their marks only and not on basis of their cast, I was ignoring one big issue that we have here, that is the cast system. Say I have 90% marks and a person from a reserved category has 85%, I used to say that I should be given preference for admission.
But what I did not consider is how I got my 90% marks and how he got his marks. I think my upbringing played very important role in this. The culture at home matters a lot. My father is a doctorate in microbiology. My paternal grandfather is a lawyer and my maternal grandfather is a doctor. Now, compare this with the other guy whose forefathers, for centuries, did nothing but cleaning of roads and gutters. So it boils down to one question, Is the development of a human being because of his nature or his nurture?
By development because of nature I mean that a human being is what he is , in spite of his upbringing and the environment which he grows in has no effect on him whatsoever. I don't think so. I believe that what goes around does play an important role in an average person's development. So crude comparison of marks is not the fair way to judge merit.
Next part is about the implementation of this concept and how can undeserving people be left out of this benefit. I think that if a person thinks that he needs reservation, he is the one who needs it badly. There will be a time when people will think that they don't need reservation. And then only we can do away with it.