Basecase said:
A can of cola can help get you through a bad patch, doesn't mean it's banned or a PED
True. I don't want to defend the rules on which performance enhancing substances are considered legal or illegal, and note that caffeine was also previously considered illegal (above a certain dose). Taking an excessive dose of caffeine before or during a marathon may in fact also increase your risk of a heart attack, and I would certainly not recommend it. But with caffeine, at least, there is a long history of safe consumption. DMAA was new on the market, and to take it before a marathon is asking for trouble. I assume that the runner did not even consider it potentially dangerous, so her death is tragic. I just hope that her example will make someone think twice, when the next "wonder pills" hit the market.
When you "hit a bad patch" in a marathon, it means you're at your limit. Any substances that promise to help you go beyond your limits, whether caffeine, amphetamines, painkillers, etc. are potentially dangerous, especially to novices.
A professional athlete (and that was the assertion in the original comment to which I replied) would never be able to "plead ignorance" about some substance inadvertently consumed with a food supplement. Rule #1, if you don't know what it is, don't take it.