I'm a regular blood donor-in fact, I'm a member of The Gallon Club-so I'm familiar with all of the restrictions, a lot of them simply targeting people who travel abroad pretty frequently, i.e. not directly related to blood-born illnesses or diseases.
It was due to mad cow. Though, I don’t know of a single case in the US.
Always felt bad with all the blood drives in the service. I imagine that they lost a few gallons of O Positive over the years.