A good friend of mine told me a story recently. Her BIL and SIL were having trouble conceiving and it turns out that BIL has no viable sperm. So she was encouraging her DH to donate. Her DH happily volunteered but his brother is still making the decision.
I was thinking, I don't think it would bother me regardless of the situation, but I know for some people it would be uncomfortable. Would you feel comfortable with DH donating sperm to someone close? To a stranger (like a sperm bank?) What if you found out that he had before you were together...?