Many people criticize the effectiveness versus the cost of sending missionaries from the West to other places in the world, particularly Short-Term Missionaries. These brief trips are painted as glorified vacations by their detractors. That's a whole other topic, though I'll say briefly that I am wholeheartedly in favor of appropriately planned short-term mission trips. The DG blog gives a brief rundown of why we should still be sending and going.
If you can't sufficiently counter each of their five points, why aren't you sending and going?