I don't know what it is like in your country, but in Israel not everyone is allowed to donate blood. This is to make screening the blood easier and more productive, as every infected sample goes straight to the bin. So they want to minimize the amount of infected blood that is donated. Therefore they restrict donators who are in high risk groups. Here is a partial list of who is allowed and who is not allowed to donate blood in Israel.

And the list goes on. I was completely pissed off the last time I went to donate (actually the one before last), and was told I couldn't, because I had been pierced. The fact that the health board approves the place means nothing to them. I was pissed off for a while, and thought I won't donate. And then I thought, that's not fair to people who might need my blood. So I lie.

Have I had any part of my body pierced? No.
Have I engaged in sex with another man? No.
Have I been to Africa? No.
Is there anything else I might want to add? No.