I would like to point out that the use of umbilical cord blood (cord blood for short) is more than merely as a source of stem cells for some future potential treatment. It is currently an extremely important source of stem cells for stem cell transplant, the only "cure" for diseases like acute lymphoblastic leukemia. The reason being cord blood contains "virgin" immune systems which causes significantly less graft-vs-host issues when compared to using blood donated from an adult.
Another good reason is that is a good backup source of *good* stem cells. Should your child be later diagnosed with some form of leukaemia, one treatment option is to wipe the slate clean and then implanting know good stem cells, i.e. cord blood. The probability of you being able to donate your stem cells for this and other procedures is low, because your child would inherit HLA from both parents, so a full match between child-parent is low. Best bet is child-child.
My knowledge of such things come from the fact I am the recipient of not 1, but 2 set of cord bloods. One from Australia, one from USA. Thanks to the people who banked their babies cord blood and made it available, I am alive today. If I had to pay for it, my family certainly would have, so you _can_ make money from it, if that is your wish. Though if you had to pay out of your own pocket, it would be a good insurance policy.
Cheers,
Steve