It's true the diagnosis for ADHD has a lot of "subjective" components in it - especially the part that involve teacher evaluation and parents observations. But a comprehensive diagnosis should not rely on just that - it should include very thorough psychological and physiological examination. When my son was diagnosed when he was 7, he had a total of 15 hours of testing (IQ, attention tests, and many more). We thought the diagnosis was a valid one and did seek professional treatment (he was on medicine for a while, but then we decided to take him off it because we wanted him to be more in control of his mind). I'm glad to say that he's functioning really well now, given the fact that he had (and still has) this difficulty. But you are absolutely right in that if your child is simply "hyper" and have hard time sitting still, it's not the reason to put them on drugs. It will do more harm than good if you think Ritalin is a cure it all:).
There is definitely an "over diagnosis" problem for Autism and ADHD in the US, but for those kids who truly have these impairment, seeking proper treatments is a must. If medicine is needed to control the symptom, then it should not be ruled out. But the important thing to remember is that medicine is not a cure, and definitely not a panecea. It's important to make sure that the diagnosis is genuine, and not just a convenient "label" given to a kid by teachers or parents, just because the kid has trouble sitting still and/or has difficulties in the social settings (in this sense, everyone really has a dose of ADHD, like you mentioned in the article).
Share two pieces I wrote on the related topic: 关注孩子的心理健康: http://blog.creaders.net/dreamweaver/user_blog_diary.php?did=9443 你愿意为孩子做什么？从自闭症，Home Schooling 谈起: http://blog.creaders.net/dreamweaver/user_blog_diary.php?did=10786
