With both my boys, we donated to a public cord blood bank. I talked with my ob/gyn extensively about this and did a lot of research. He said (and I found out myself as well) that most diseases cannot be cured with a person's or a close family member's own cord blood, as they would also be genetic carriers for the disease. (Yes, there are stories where a family member's cord blood saved someone, but those are very few and far between.) But for many people who do have a disease that could be cured by cord blood, there are not enough stores to have as great an effect as there could be.
Because cord blood is so versatile, each packet could save several people, whereas if it was banked by a private company, there could be several people that would have no access to those life-saving cells.
And because my children are bi-racial, and several diseases are found more in one race than another, the demand for my children's cord blood was really quite high in the area where we delivered.
I would recommend looking into a public bank. I know there is one in Saint Louis, as we delivered there. I know that there are more opening every year. From where I see it, it is very selfish of me (and expensive, too!) to bank something that has the potential to save several people.