At the time of the 2004 election, Facebook was open to students at some US universities. So to the extent the Obama campaign used Facebook at all it was the first national campaign to do so.
Every major campaign was using Facebook in 2008. To give the Obama campaign credit for being the "first" when it was used THROUGHOUT that primary by both parties at the national level and also at the state/local level makes no sense.
That said, Facebook organizing in 2008 looked nothing like what it looks like today. It looked far more like what we were doing in the MySpace days as far as political organizing online (MySpace got about the same amount of traffic back then). I personally think their work with MyBO is more noteworthy and distinguished from what other campaigns were doing, even if it wasn't built by them.
