I am so pleased to see this thread! I am a medical technologist and have been blood banking in hospital laboratories since 1980. So much has changed in those years- unfortunately the number of people donating has NOT increased.
However, thank goodness for the folks who do (or have in the past). When people ask me if they have a "rare" blood type, I always tell them that the most rare blood is the one that isn't sitting on the shelf in the BB refrigerator when I need it!
Also, if you can't give blood, you can help those who do donate by covering their job at work for an hour while donating (at an on site drive) or even volunteering to help at a local drive.
All of the pre-donation questions and limits may seem a bit bewildering but it all has been studied and thought out to help protect the blood supply. Also, they really help protect the donor.
Many folks don't realize how strictly regulated blood is- the FDA is stringent in all areas of handling the product. Unlike television (such as "ER"), doctors do NOT do their own crossmatching and do NOT just run into the blood bank and snatch blood off the shelf in an emergency!