It might, just might save your baby's or another family member's life at some point in the future
You will only have one chance to bank your baby's cord blood; the moment immediately after birth.
The cord blood collection process is simple, painless, and harmless to the baby and mother.
30%-70% of people who need bone marrow transplants can not find a match. Finding a proper match is especially problematic for African-Americans, Hispanics, Native Americans, and people of mixed ethnicity. By banking your baby's stem cells, the odds of having a proper match for the baby or another family member improve.
Especially beneficial if a family member has a condition that can be treated with a stem cell transplant, such as sickle cell anemia, thalassemia, aplastic anemia, leukemia, metabolic storage disorders and certain genetic immunodeficiencies.
Future medical advances might allow stem cells to treat even more diseases and be used in more tranplant cases than current medical practices.
I've tried to summarize the argument for banking cord blood as succinctly as possible. If you visit the sites of various cord blood banks, you can find out some useful information. Each bank has a detailed (although biased) argument in favor of blood banking.