Cord Blood Banks are not a scam. I work at a bone marrow / cord blood registry and i can guarantee that these units save lives. However my situation is somewhat different from TFA as i work to find unrelated matches. For the related donor circumstance there are many uses for these cord blood units within your family or for the original donor. I feel i should give a little insight on each of your bullet points as you seem to have the idea but not the full perspective.
1. Yes, you can obtain Peripheral Blood Stem Cells (PBSC) however if the donor themselves is sick then the stem cells they are producing are not useful so the umbilical unit would be used for a fresh/clean source of stem cells.
2. Though you are correct that there is a low chance for this to be useful within your family can you imagine if you were part of the percentage that it was useful for how thankful you would be. The chance drops even lower when you consider that it's possible that no one in your family will get sick from a disease that stem cells would be useful to cure. However if you did need this sample it would be presumably a better match for a family member than an unrelated donor, which would be one of the few option for you. The other thing to consider on this point is that sometimes a perfect match is not what physicians are looking for so a guaranteed match on a number of antigens, a sibling has a very high likely hood of matching some of your antigens, might be more beneficial than an exact match.
3. Life has no guarantees. However Cord blood banks have a lot of experience storing these units. They are stored in countries all over the world and in 5 years of coordinating testing and transplantation of these units the only cases of unusable units have been caused by transportation issues and never storage issues.
4. Yeah there will be more stuff you can do with stem cells someday but today there are still many uses for those stem cells.
5. You say by then but consider the situation of a person i really know. He contracted Leukemia from over exposure to gasoline as a child, while build race cars with his father. He had to go through the process of unrelated bone marrow search, however if he had had his cord blood unit banked his physicians would have been able to transplant from that unit.
6. This is the only point i can't speak to. In the unrelated bone marrow world all units stored are matched against all the patients world wide. From your description it their sales men sound slimey, however not really lying, just playing up the benefits and the guilt.
I'm not advocating storing Cord Blood units for personal use but people should not think they are without merit.