It’s a torn issue with me too. I’m a parent of an ADHD child. My nephew was also diagnosed some years before my son was.
In my nephew’s case, I’m not sure he needed it. After he was put on medication, he seemed to not care about anything anymore. It broke my heart. We lived several states away, though, so I’m not in the loop on what he was prescribed at that point. I believe they changed his meds, and he has since grown up to be a well rounded young man, with energy and focus, so his story has a happy ending.
My own son was diagnosed when he was 7. It was his teachers who suggested it. My husband and I were very much against medication, and we tried the therapy route, changing his diet, etc. It wasn’t working, and we broke down and let the doc prescribe Concerta, after two incidents in which his spontaneous combustion came too close to seriously injuring other children. He would throw things without regard to those around him, and one incident involved a pair of scissors. We knew we had to do something, and the usual parent intervention wasn’t working.
It worked for him, but he became much more emotional. We drew the line, when the doctor wanted to up his dosage and also prescribe an anti-depressant, after asking leading questions to get my son to say he felt hopeless.
The Concerta really did seem to help, though. He’s turning 13 this month, and has recently been switched to Adderall. His dosage has recently increased, which causes me some concern, but we’re monitoring him closely as well. It helps that his new doctor listens to us and our concerns, and helps us deal with the day to day questions.
As a parent of a pre-teen, it’s difficult to know when the ADHD is causing something, the medication is causing something, or his raging hormones are running out of control. 
I can see a less educated or less concerned or less active parent missing signs that something isn’t right, especially if they’re dealing with a teen or pre-teen kid. What’s normal teenage behavior, what’s flat out defiance, and what’s a lack of focus or memory? Those lines are not always clear.
Combine that with a doctor who has an open prescription pad, and it can be a fatal combination. But I simply cannot see medicating a child at 2 or 4. Even kindergarten seems too young to me. That’s when those who haven’t had a daycare experience are LEARNING how to socialize, get along with people, consequences of actions on a SOCIAL level. How can anyone know what goes on in the mind of a child that young?
Our ultimate goal with my son is to keep working with him and teach him ways to overcome his lack of attention span in other ways. Medication is great stuff, for a variety of mental issues, but I feel that it does no good if it’s the only form of therapy. If I break my leg, I can use a crutch to get around, but that doesn’t excuse me from doing physical therapy type stuff to keep it strong, when it’s healed enough for me to do so. That’s just me though.