Comment 2 for bug 317258

For Launchpad itself, about 90% of duplicates are duplicates *precisely because* the person reporting them was looking in the wrong project, so they are correctly marked as duplicates of bug reports filed in a different project. Granted, that is because Launchpad abuses multiple "projects" for a single project, but I expect similar issues occur with bugs in Bazaar vs. Bazaar plug-ins, Xorg vs. individual video drivers, network-manager vs. wireless drivers, gnome-power-manager vs. the Linux kernel, and so on.