I know that article is talking specifically about MDMA, but I think the dangers of ecstasy are more due to the fact that in recent years it doesn't actually contain much MDMA and instead uses much less understood chemicals, which are probably more dangerous than MDMA would be.
You're mistaken. The metabolites of seratonin, in excess, are neurotoxic. MDMA works a vesicular releaser, flooding the space between cells with the neurotransmitters that make you feel good. As the brain metabolizes the recently released flood, waste is produced. The brain can healthfully handle a certain level of waste, but beyond a certain level and you risk cellular death. However, this suggests that low doses of MDMA may not pose a significant risk.
This is how it was explained to me during my "Drugs and Human Behavior" class 5 years ago at Drexel.
