With over six billion people on earth and about two billion internet users, the world is getting overwhelmed by data which has really been on the rise since we began the social and participation era in computing. Therefore, there's a high chance that the data for the chart you want to present is out there behind one RSS feed, RESTful service, or some sort of API call that will produce either XML or most likely JSON formatted data.
You may want to know how much your country owes the World Bank or what the emission/pollution ratings of your country have been for the past five years. I decided a good example will be to plot how many Nigerian primary school children are out of school over a certain period of time with a line chart having two line plots, one for male and the other for female children, so that at a glance we can tell who is worst hit.