Hubby and I both agree neither of us could ever donate sperm or eggs, I just couldn't emotionally cope knowing there were children in the world that were mine, I know there's a lot more to being a parent than a biological link and obviously know their adoptive parents would be their parents in every sense of the word but I still couldnt emotionally detach myself from the situation even if I knew nothing about it all.
I would consider being a surrogate for a close family member or friend if desperately needed and so long as it wasn't my egg I know I wouldn't be overly emotionally attached and could say good bye. I wouldn't feel like that if I was directly related.
Obviously it's amazing that there are women out there who do it to give other women the opportunity to have children, in the UK as far as I'm aware it's not really something you can do for financial gain, I believe you only have the costs incurred to donate so your travel expenses and leave from work paid etc, I think it's a bit questionable morally to do if for money.
I've never heard it interfering with fertility and certainly wouldn't do it more so before having children.