Though spending on civilian protection did increase in part because of our advocacy, as Mr. Gustafson notes, it has been necessary.
The UN Security Council authorized the AU-UN Mission in Darfur (UNAMID) in July 2007, because an under-resourced, outgunned AU protection force was on the verge of collapse. The AU force had neither the experience, the infrastructure, nor the stable funding support necessary to run a mission in Darfur. That such a mission was undertaken at all is a testament to just how violent a place Darfur remains, and just how critical civilian protection is to stability in Darfur.
Darfur's recent history is littered with failed cease-fires, and the April 2004 N'Djamena cease-fire agreement is sadly just another example. Were it in fact as successful as Gustafson claims, one wonders why new cease-fires were deemed necessary in subsequent years.
Civilians are not safe; in particular, rape remains endemic. And that lack of security is also a major problem for the humanitarian operations on which 2.7 million displaced Darfuris and another 1.3 million "conflict affected" civilians depend in order to survive.
The government of Sudan, which bears overwhelming (though not sole) responsibility, is certainly unwilling (and at this point probably unable) to provide the necessary security. That leaves it up to the international community, which means that the US needs to play a leading role.
Needless to say, neither Save Darfur nor the US government established the size of UNAMID or drew up its budget; the UN did. It is worth saying, though, that Save Darfur's advocacy efforts have helped convince the US to provide hundreds of millions of dollars in additional bilateral peacekeeping funds over and above the standard US share of the UN peacekeeping budget to help develop and deploy the force.