The paid tours of Millenium Villages that I mentioned earlier set the (relatively tiny) development blogosphere ablaze. This isn't totally surprising: it's a difficult issue to approach with nuance. I stumbled upon a unreasonably thoughtful article in the Christian Science Monitor. For an even better discussion, see the Scarlett Lion's interview on township tours in South Africa.
I'm still not terribly convinced that poverty safaris are a great idea - even if we ignore the possible incentive problems, I highly doubt that touring around a village with a large group of azungu would give you an accurate idea of what life is like for the poor. Still, it is relieving to see a more nuanced discussion than we've seen so far (see comments).