Here is a comment from Tim Challie's Blog

"There is a time and a place for humanitarian work, no doubt. Christians can have great ministries serving the poor and the oppressed and in so doing can have remarkable opportunities to share the gospel. And yet still the history of Christianity shows that when Christians do this, the gospel quickly becomes secondary and the work itself becomes the gospel. I still see the Bible primarily emphasizing charity given to other believers; when I look at Acts and the epistles, this is what I see most—Christians helping other Christians as a sign of love and fraternity. Now of course there will be some who engage in humanitarian work outside the context of the local church, but it seems to me that the closer we come to making this a necessary part of the Christian mission, the more likely we are to see the gospel diminish.”

I'm inclined to disagree because I'm not sure if you can separate humanitarian work from the Christian mission.