My gut feel is that statistically, more people on here would be blood donors than another population sample.
My reasoning is that as a rule, people here are generous, think of others when in need (Miles888 for example) and are just generally all round good eggs.
As we also like to play with sharp things it is sensible insurance to have some in the bank as it were.
Now prove me right; or not...
I have been a donor for 30 years just to kick things off.