I propose a compromise to resolve the marriage debate that I think everyone should support. It is based on the univerally acknowledged need for same-sex procreation to be thoroughly examined and declared safe before allowing any lab to attempt to create a person that is not the union of a man and a woman. Until same-sex conception is declared safe and acceptable, same-sex couples should not have a right to attempt it, and this difference in rights from both-sex marriages (which all have a right to attempt to conceive) would simply be acknowledged in name. If and when same-sex conception is considered safe and Congress decides to allow same-sex couples to attempt to conceive, they will do that by changing same-sex civil unions to marriages. Marriage will continue unchanged, always granting the couple conception rights.
In return, the federal government would officially recognize state civil unions as if they were marriages, including paying the social security and tax benefits that the federal government gives marriages. (and the federal government could encourage all states to offer civil unions, since their main objection (that they are marriage in all but name) would no longer be true)
The "tradtitional marriage" side would get to preserve the word marriage, and clearly differentiate it from civil unions in the most substantial way, preserving equal conception rights for all people and preventing unethical manufacture of genetically modified people. This would ban reproductive cloning also, effectively ending that debate as well. (It would not affect the debate about therapuetic cloning, as that does not attempt to create people). The cost of federal benefits for civil unions would be quite minimal, though it certainly is a cost.
The SSM side would get federal benefits and a much greater liklihood of civil unions in all 50 states. They would only give up something that is not even possible and might never be, but they would give up the pretense that same-sex couples have equal rights to both sex couples and acknowledge that people only have a right to conceive with someone of the other sex.
The people who do not support this compromise should have to convince us that, depending on why they don't support it, same-sex couples should be allowed *today* to attempt to conceive children together in spite of the risks, or that committed civilly-unioned same-sex couples should not be entitled to federal benefits.
Update 2/14/2013: This was the original proposal of the Egg and Sperm Civil Union Compromise in 2006. It is still the same, except now I specify that Civil Unions would have to be defined by the states as "marriage minus conception rights" to receive federal recognition as if they were marriages.