Other connecting points
Globaliser, I think I didn't make myself clear. I agree that if you're connecting to a point in the USA you have to go through check-in, security etc again the critical point about Atlanta (and one or two other airports in the USA) is that it doesn't matter whether you are connecting or simply going to landside you have to go through security.
If you consider Chicago as an example of an alternative you go through immigration etc and, yes, as you exit customs you can re check your bags immediately if you choose to but at that point you are landside. If you chose to you can simply wander off into the USA you don't HAVE to get on another piece of equipment to do so. Yes, you then have to get transit from the international terminal to one of the domestic buildings but to do that you don't have to go through security - that happens in the domestic building. In Atlanta, as you exit customs your next step HAS to be security, no exceptions.