Just to be clear: when I said "pool", they don't like, blend the blood--I just meant that your bag of blood is available for general usage. They can and do track individual packs.
Regarding the postcard: I have donated in Illinois and California and have never gotten one. But I haven't been able to donate for a few years now because of trips into malaria zones, so if this is a recent thing, that would explain it.
That would most likely result in another blood contamination scandal similar to [http://en.wikipedia.org/wiki/Plasma_Economy] in Henan China, where blood was mixed in centrifuges to save cost, subsequently infecting large amounts of the affected population with HIV.
But i had that image in my head as well, a big dirty vat of blood somewhere in a dipilated factory building.
I know for a fact that in France they test every single donation, since the "Contaminated blood products" scandal affair in 70'. They even use a 1000++€ AIDS test which can detect HIV within a 3-week time span, instead of 3 months.
Thanks the blood donation tests, I found I had a punctual lack of iron earlier this year.
I donate blood to Red Cross in California (most recently about a month ago) and have also never gotten a postcard, but they do have a pretty cool app now (called "Blood Donor") which tracks your donated blood through the various stages of their system (processing->testing->storage->distribution).
I'd assume any postcards sent out probably happen at the distribution stage, when the blood is shipped out to a hospital as that is a close enough approximation for the time when it will be used.
My local blood bank (in northern Virginia) has sent out post cards when my brother's, my father's, or my blood have been used in a donation. We're only O-, so not super rare but the blood bank does call if we've gone a while without donating.
