Here is another interesting graph: Package Dependency graph of Gephi's trunk with the node size linked to the number of bugs detected by FindBugs (
http://findbugs.sourceforge.net).
Regarding the types of bugs, most of them belong to the Style and Performance categories.
The winner package is: org.gehi.statistics.plugin (51 bugs reported)
The winner class is: org.gephi.ui.timeline.plugin.drawers.minimal.MinimalDrawer (10 bugs reported)
And finally, the winner method is: org.gephi.branding.desktop.reporter.ReportController.logMessageLog(Report) (4 bugs reported)
If you want more details, I'll be happy to send you the Graph file.