Most of the misdiagnosed are in younger kids that parents cant control so they automatically assume that it is ADHD. When really it is lack of good parenting.
Its often a far far more complex issue than that. Parents might play a roll, but so do things like a school system in decline, kids living in terrible neighborhoods, massive funding cuts that are closing services that kids need, overloaded teachers etc etc etc...
I wish it were as simple as some want to make it, but it just isn't. Sad thing is, it is getting worse and by the time it gets very bad it will be too late.
I am an early case of ADD (diagnosed in the late 80s) and underwent two weeks of testing (my parents were opposed to putting me on stimulants and really wanted to be sure). I have been off and on ADD meds for quite some time. I didn't like them as a child. Also, I have tried some of the non-stimulant meds and reacted very poorly too them. I took Straterra for two days and got off, the next day was when the first reports of suicide came in. I didn't feel suicidal but had some really weird ideas popping in my head.
Stimulants still speed me up, but I hardly ever take them.