First, I should say that I'm just considering this idea right now. I may not do it.
I had an idea for a blog that I thought I'd run by people here to see what everyone thinks: an atheist (i.e. me) visits different churches/temples/etc., sits through their services, and then writes about the experience.
The idea wouldn't be to be sensationalistic (i.e. no freak show of "hey! Look at the weird stuff that these people believe!"), but I wouldn't plan on glossing over negatives, and - judging by my experiences in church - there's likely to be some negatives. Instead, the idea would be to give a different perspective on what goes on.
I've seen writing projects where atheists or other outsiders actually joined a church and participated as members, only to tell the congregation later that they'd been duped, and that a book or blog was about to come out. It seems like that approach causes a lot of hurt feelings - it wouldn't be the approach I would take.
Instead, each blog entry would be on a single visit to a place of worship. My plan would probably be to not advertise what I was doing... I'm still deciding what to say if asked. Either I could come clean right away and say what I'm up to (which would probably make people change how they behave around me) or I could give them a cover story: either that I'm considering the denomination/religion (which would also probably affect how they would behave around me, and be misleading if not a full-out lie) or that I'm a member of the denomination/religion visiting from out of town (which would create a huge workload of studying beforehand, as well as be, well, a bald-faced lie).
So... what would you think if your church showed up in my (potential) blog?
What would you think if, on reading it, you realized that I had lied to you when I told you that I was "one of you" while I was there?