Coming from the UK where circumcision just isn't done other than for religious reasons, I have to say that I find it so strange to think that in the US (and some other places) it's the norm. It's just unimaginable to me.
I'm going to put religious reasons to one side as I can't argue something I know nothing about. But unless it's for religious reasons, I must say that I just can't see why you'd do it:
1) It's cleaner and healthier - if this was the case, then surely countries like the UK who DON'T circumcise as standard must have thousands of cases of willy-related problems left, right and centre? And I'm pretty sure this isn't true! Willies are willies - keep them clean and chances are everything will be fine. And if not, then deal with it at the time. Don't cut it off at birth "just in case!" (which leads me to my next point..)
2) It's done as a preventative measure - ??!! So a newborn baby has it's foreskin cut off because he MAY have a problem with it at some stage in later life? Why stop at foreskins - why not remove tonsils/appendices at birth as well? The fact is that most uncircumcised men never have any problem - just educate people how to look after them properly (i.e. DO NOT RETRACT THE FORESKIN BEFORE IT IS READY).
But I know it's easy for me to say this because I come from a country where my friends would think I'm totally mental if I circumcised my son. If it is the norm to have it done, and you're always told that it's the right thing to do, that it's cleaner/healthier etc etc then I do see that people just follow what's normal.