This is the third thread I've seen on cord blood banking, and I'm beginning to wonder if I am missing something. Generally, the consensus is that there is no point in doing it, and I am left scratching my head. I won't retype my earlier arguments for doing it, because I'm sure that can be searched, but in short: a) medicine creates miracles daily, and you should not judge potential uses 18 years down the road by today's; b) as a way of an example, ten years ago they have already shown that stem cells can heal the heart muscle after a heart attack - something a good chunk of us may experience; and c) as a way of another example, the work on 3D-printing artificial organs and populating them with person's own stem cells is just taking off. Of course, by the time that work is done, stem cells will likely be derived from adult tissues, but that is also a work in progress.
Just as a comment, some of the private banks will refund all your payments in case that your child's blood is needed but unusable. Still a good business plan for them, as most will never be used, but it's nice to know.