I have previously written quite a lot about circumcision. See for example (1) here, (2) here, or (3) here. Circumcision proponents use different arguments when they try to spread this surgical procedure. Sometimes they say that your hygiene benefits, which may be true if you never ever clean yourself under the foreskin - hardly a reason for removing the foreskin. Another rather medievil argument is that circumcision will make it harder for the child to masturbate, and after all sexual pleasure is something you should avoid!
The only potentially valid argument for the use of circumcision, an argument which has only been around for perhaps five years (before that circumcision was conducted for irrational reasons entirely), is that it may reduce the risk of getting HIV if you have unprotected sex. Based on this some people argue that we should use mass circumcision to prevent the spread of HIV. There are many arguements against this.
First of all, people normally don't make their sexual debut when they are still in diapers, so let them choose themselves whether they wan't to be circumcised when they have reached an age where they can actually make such decisions. Secondly, condoms work much better than having your penis circumcised, so why not spend all the money advocating the use of condoms and handing them out for free instead? Furthermore, people who have been circumcised may feel safer and therefore have more unprotected sex, thus cancelling the potential gain...
Another serious argument against circumcision is that circumcision may cause serious problems for the patient in terms of penile function and penile sensitivity. The foreskin has a lot of sensory nerve endings. According to estimates that I have read, 50% of the nerve endings in the penis are in the foreskin. Just recently a study investigating the consequences of circumcision came out.
The study seems to show that people who have been circumcised do not suffer from reduced pleasure, at least that is what they say. However, as Mary Crewe points out, studies like these do not take into account psychological biases which are very likely to be at work. If you go and have yourself circumcised (the people in the study voluntered of course), then you will want to justify that decisions afterwards. As a result, minor troubles are likely not to be reported. The patient will simply bite together and say "I am fine, and my sex life is great".
For this reason I think it would be a mistake to start circumcising people based on this type of questionnaire evidence. Some sort of medical examination of penile function (or dysfunction) would be preferred.