Why not? Donating bone marrow is an act that costs nothing to those who give and gives an enormous amount to those who receive. It’s simple, it’s right, and it’s rewarding.
If this isn’t enough, consider this: in order to have a transplant a compatible donor is necessary, and the probability of finding one are roughly 1 in 100,000. This means it’s a slim chance, and even one person more could really make the difference.
The stem cells of bone marrow are the only way of curing a great variety of diseases (that are often fatal) such as the various leukaemias, thalassemias, solid cancers.
It is for these reasons that becoming a bone marrow donor is right (and great!): the more the donors, the more the people whose lives can be saved.