That's what I said too.
The issue is ENFORCEMENT.
Short of Impeachment or the Withholding of of funds, there is no mechanism of enforcement. A POTUS can still act as he chooses.
There is one more way - the ballot box. The blacks [who are in the majority] in DC are already pissed off that the DC Council passed gay marriage over their objections [the blacks are mostly Southern Baptist]. They are also REALLY pissed off that the question was PREVENTED from going to referendum in the last election.
Now, with Obama NOT defending DOMA - I think they are gonna be REALLY REALLY pissed off ...
Don't know what it will translate to in 2012 though ...