Sperm donor rights?

I listened with great interest for my lesbian and single-mother-by-choice friends who used donors to this morning's radio program, Forum: Should Sperm Donors Have Parental Rights?. The upshot appears to be that you must work with an experienced attorney to draw up your contract if you use a known donor, and you must abide the terms you describe in the contract for it to hold. Children have a right to know their biological heritage, and most people are honorable. But being a "daddy" takes more than a donation of DNA and/or money.