What are the legal implications of sperm donation?

The laws concerning conception vary depending on jurisdiction & the method of insemination (private vs physician supervised). One example would be a sperm donor automatically waiving their parental rights unless a contract is agreed upon. Another example would be a sperm donor becoming legally responsible to pay child support, even though the involved parties have an informal agreement to the opposite. It would be prudent for any involved party (donor or receiver) to at least get guidance from a medical physician specialized in this area.