The Ship of Fools website performs a valuable service in lots of ways - deflating pomposity, pointing out some of the more absurd directions in which "Christianity" is moving, and so on.
However, I would like to quibble about the "mystery worshipper" concept - as it was also found in the Ruth Gledhill column in the Times for a good few years (don't know if it still is). Churches certainly ought to be doing what they can to make visitors welcome. Their meetings ought to be accessible and clear. The teaching should be relevant. It's not the pursuit of these aims that I would take issue with. What I don't like is the thought that, rather than going into a church expecting God to speak to me, the mystery worshipper is going into a church expecting to judge it - and that many of the people reading the reviews are also effectively sitting in judgement over the churches. It rather misses the point that we become part of a church community so that God can speak to us through his Word, and so that we can build one another up and encourage one another. It's all good fun and all that, but the whole idea that church can sit so lightly on me that I can go in, watch what's happening, come out, and jot down a few humourous comments before going to another church next week is a rather damning indictment of the post-modern Christian concept of a church.