The premise was essentially that we as a society have been taking caffeine since the beginning of the Industrial Age and that life today is different from that of a 19th Century factory worker so we may want to re-evaluate whether the drug caffeine is still useful to us. I'm not really sure how the contents of the talk, which was all about caffeine, fits the title of the talk or the 'agile' track it was in.
She started by highlighting that before the Industrial Revolution, Europeans tended to have beer for breakfast - since water wasn't really safe to drink. However of course that didn't really lend itself to the regimented and time controlled practices required in a factory at the beginning of the Industrial Age. Tea and coffee became popular at about that time, she posited, because it could help us get up with the clock rather than the sun.
The main part of the talk was about the metabolism and concentration of caffeine in the body and discussing some studies that show that while caffeine is good at helping people concentrate on simple and long running tasks (such as those required in a factory), it has no extra benefit in terms of the sorts of tasks that software developers do. In particular she highlighted some of the issues regarding how caffeine effects are based on concentration in the body, and pointed out that drinks often marketed at children can have high levels of caffeine in them: that we "learn" to drink caffeine at an early age where we would be alarmed at giving children other drugs. This was indeed food for thought and I agree with her that perhaps we as a society ought to be re-evaluating how much caffeine we drink.