In 2005, Britain changed the law protecting anonymous sperm donors and allowed children to learn the identity of donor fathers (which is bad news) and limited the number of women who can use sperm from one donor (which is good news).
In 1991, Britain registered some 500 sperm donors; since the change in the law, the numbers have dropped by 40%. Obviously, the men were anonymously donating sperm for the financial compensation, and not for the purpose of fatherhood. Once the anonymity factor was gone, motivation declined as these men likely felt threatened by potential future responsibilities to a child they had no intention of taking any responsibility for; either financially or emotionally.
Another concern about anonymity is the sanctity of the family. I have always advised married, infertile folks who have called my program to keep their plans a complete secret. I don’t believe it is in the best interest of children to have a sense that the wonderful man protecting, providing, and loving them is not their daddy. Anything which interferes with that child/father bond should be avoided whenever possible. And, I never thought the origin of the haploid DNA contribution was as significant as the ultimate parent/child relationship.
Britain capped the number of babies which can be created from one donor. Sperm from one man can now be used to produce only 10 babies (in Holland the number is 25). The United States does not cap sperm donations at all…and I think that is ridiculous. You certainly don’t want anonymous sperm in one geographical location to be used to make scores of babies who are unaware of their genetic relationship. The statistical probability of them meeting, falling in love, marrying (aw, I’m such a romantic) and then having children is not insignificant. This is a factor that could lead to obvious medical problems for their offspring.