In my Sociology of Religion course we recently finished Christian Smith's American Evangelicalism (a/bn). The book is really good; it's one of the few books that, as I read and had questions, eventually answers them. Although sociologists talk about a general secularization of society, what we see in everyday life is that religion is still very much alive. Smith's book looks at why this is, and he forms his subcultural identity theory based on an earlier secularization theory of pluralism. One of Smith's idea is that, looking at religion as a competitive market, the "fittest" religion gets the largest congregation.
This idea, although a little heretical at first, actually has a lot of merit. I highly recommend Smith's book for more details, but one of his points is that a changing religion doesn't equate to a religion giving ground to science; it's merely adapting to what society wants. This would be equivalent to businesses trying to brand differentiate; it's merely a strategy (albeit an unconscious one) to survive.
The idea of mapping one domain to another is old. This is the most obvious in mathematics: Godel's proof of incompleteness rests on mapping the metamathematics language (or any formal system) back to mathematics itself. It goes back further, however, with Descartes. In modern times it seems natural do talk about geometry in terms of x and y, but such a mapping between geometry and algebra was not always obvious to mathematicians. The main idea is that mappings, provided they are correct and you know the limits of any particular map, provide new perspectives on looking at the original domain.
For example, the mapping of religion to economics suggests price discrimination within a church. And with megachurches, we do see that: people can walk in and walk out on Sundays only, or they can join the plethora of prayer groups, social outreach projects, and other activities offered during the week. To each his own; if someone is willing to spend time (more on this in a bit) working for the church and strengthening it, the church will draw them in. They are the consumers at the left end of the demand curve, willing to pay a large sum for religion. For the others who are not as interested, well, they can just come and count towards congregation numbers.
In class we talked about how although in society there are lots of religions to choose from, the background of a person might prevent them from choosing their favorite religion. For example, if someone was raised in a fairly restrictive church, and grew up thinking that way, it is likely that they will stay within that church. They simply do know enough about other religions to make a choice. This makes me think of complex systems, and the general problem in economics of information flow. The general assumption of perfect information is clearly too idealistic; what happens when consumers don't know that on the other side of town you can get the car for much cheaper? Joshua Epstein and Robert Axtell's Growing Articial Societies deals with this a bit. I actually reconstructed their models for a project last quarter, and their conclusion is that while the market does head towards equilibrium price, it takes time. Through in changing preferences and difference in taste between generations, then the economic equilibrium is almost never reached at all. What does this say about religion? Well, there's probably people who would join a church if they required less ("dead weight loss"); people will probably keep changing churches; a single church won't dominate the entire religious market... You get the idea.
The last "map" I will make, although this is not so much a map as a "reminds me of", is to psychology. Smith suggests that with the large number of religious choices in society, people are more likely to find one they like and commit to it. Psychology, however, suggests otherwise. Sheena S. Iyengar and Mark R. Lepper has written papers on how people are more likely to buy jam if given 6 choices instead of 60. This NYTimes article gives a non-technical overview. While this does not invalidate Smith's theory, more research should perhaps be done on choice between religions.
For those who find domain mapping a valuable tool, it might be interesting to you that these metaphors - which are what maps are when you explain them - have been considered by some (in particular, George Lakoff) to be the basis of how we learn. The metaphors also suggest certain attitudes. I used the phrase "spend time" above, seeing time as money. Does that mean I look at time as something I "own", that I should maximize my time, and there's only a finite amount of it?
Lakoff's book Metaphors We Live By (a/bn) will probably give more details on this. I have yet to read the book either; I would gladly read it with you and discuss.