When adjusting the aggregation limit on MultiplePiePlots, setting the value to zero results in the tooltips for all columns displaying on all charts.
See the attached example.
Email: bkrisler <at> bbn.com
An example demonstrating the bug.
Logged In: YES
Thanks for the report, and extra thanks for including the sample code. This isn't a bug - take a close look at your dataset, and you'll notice that it has two columns and *twenty* rows. In each column, half the data items have no specified value, so 'null' is assumed. By default, the PiePlot will display null values in the same way as a zero value - you can override that behaviour, and have the plot IGNORE null values, as follows:
MultiplePiePlot plot = (MultiplePiePlot) chart.getPlot();
PiePlot subplot = (PiePlot) plot.getPieChart().getPlot();
JFreeChart Project Leader