This just reinforces what I have been saying for years; the government should never have gotten into the "marriage business" in the first place. Marriage should be a matter of faith and spiritualism and not subject to government definition. The govt should only be involved in civil unions (basically Partnership Agreements or "Household Composition Contracts") for any group of 2 (or more) consenting adults without discrimination of any kind and solely for secular purposes of taxation, determination of guardianships, inheritance, etc. When businesses have to discriminate just to comply with secular law, the system is broken.
Plus, this approach to civil unions would also provide an option for (for example) a lesbian couple with a child to form a union with the bio-dad for purposes of residency, parental/guardianship rights, etc even though there is no romantic or spiritual relationship between the bio-dad and either lesbian partner. Other such examples also come to mind; there are lots of legitimate reasons to form a family unit as a civil union that have nothing to do with love or sex.
If the Repubs are smart, they will side with the anti-DOMA corporate world on this one.