Here is an interactivity post I did for one of my classes recently:

I suppose only God truly knows how effective short-term missions work really is, regardless of our experiences and studies that asked this question on the field. This should truly be evaluated on a case-by-case basis. There are so many different factors involved to determine an answer that make it difficult to answer. What do we mean by short-term? Is it 2 weeks or 2 months? Where is the trip? What is the spiritual climate like there? Is it a third world country or relatively wealthy? What cultural barriers are present for Americans or other foreign cultures there? Who organized the trip? Was it a church or a sending organization or both? What was the purpose of the trip? Was it to aid missionaries temporarily? Was it to help translate? Was it for social justice or human aid causes? Was it to teach English? Was it to train leaders theologically? Was it to share the gospel with musical or drama presentations? Was it to share the gospel through Bible studies and preaching? Where they helping to plant a church? Where they doing medical work? Construction work? How many people were on the trip? What kind of education or aspirations do they have? What were their goals in being there? How long have they been a Christian? Where are they in their spiritual development? Does the team like each other and get along? Do they speak any foreign languages, particularly the one the nationals speak on the trip?

These questions are barely scratching the surface. We even need to ask ourselves what we mean by effective, because the effective results of a trip can be totally different from the intended purposes. Of course this is often heard in the sentiments of most people who have gone on a short-term trip as most say they were effected far more than they thought they were effective. For this particular reason alone, it is enough for most to justify the existence of short-term trips. Rarely does anyone ever regret taking a short-term trip, and even rarer are those on the field who regret having had short-term missionaries come. Surveys do show that almost all of the foreign missionaries on the field today (particularly from the US) are there in part as a result of a short-term missions trip. This is not to say that there are not shortcomings of many short-term trips, but as long as it serves to expose potential long-term missionaries to work in the field, I would say they are highly effective in serving the global missions movement.