I think that since the attacks on the United States, airport security has stepped up to another level. There has not been such an attack since then. Airport security has become more caution and upgraded security measures and technology to prevent these things from happening. Security scanning machines are more advanced and can basically find anything that could cause harm.
I believe airport security scanning machines are safe and somewhat effective. They don't do all the work, so there is room for human error. Flying seems to be more secure with these processes but they are a pain to be subjected to. It's unfortunate that this type of thing is necessary.
While airport security scanning machines do emit radiation, they do so at extremely low levels. They are potentially embarrassing, but they also prevent people from getting on planes with items that can cause problems. While invasive and uncomfortable, they do make flying safer for everyone involved in going through them.
Airport security scanning machines are very safe and effective. They are becomming more high tech as time passes, too, and a little less intrusive. There is one where you stand in it, put your arms up, and get a full-body scan done. It takes but a few seconds, and you're on your way.