Here are two semi-related articles: one by William Easterly about how aid to Ethiopia is propping up an oppressive regime, and another by Rory Carroll on the pernicious but well-intentioned effects of aid tourism in Haiti. Basically, it's really hard to do things right, because international aid and development are not simple. Good intentions are not enough. You can mess up by funneling all your money through a central regime, or by having an uncoordinated, paternalistic mess.
A couple confessions. First, I'm a former "aid tourist." In high school and college I went on short-term trips to Mexico, Guyana, and Zambia (and slightly different experiences elsewhere). My church youth group went to Torreon, Mexico and helped build a church (problematize that). In Guyana and Zambia I was part of medical groups that ostensibly aimed to improve the health of the local people; in hindsight neither project could have possibly had any lasting effects on health, and likely fostered dependency.
Second, I'm an aspiring public health / development professional, and I'm afraid. I don't want to be the short-term, uncoordinated, reinventing-the-wheel, well-intention aid vacationer -- and I think given my education (and the experience I hope to continually gain) I'm more likely to avoid at least some of those shortcomings. But I'm scared that my work might prop up nasty regimes, or satiate a bloated aid industry that justifies its projects to sustain itself, or give me the false impression of doing good while actually doing harm.
I think the first step to doing better is being afraid of these things, but I'm still learning where to go from here.