Bug 544055 was filed by ABRT, and I manually marked it as a duplicate of bug 540810. However, since then, numerous people have added themselves to the CC on the former bug; see https://bugzilla.redhat.com/show_activity.cgi?id=544055 I asked, and according to https://bugzilla.redhat.com/show_bug.cgi?id=544055#c4: "abrt claimed that this problem had not been reported before, so I filled in all appropriate info. I am surprised it did not create a new BZ but attached to an existing one. Looks like a bug, indeed." So it looks like ABRT is detecting virt-manager crashes, and somehow detecting that the crash is a duplicate of bug 544055 (perhaps via analysis of the stack trace?). This seems surprising to me; I believe that it would be better if it detected that 544055 was marked in bugzilla as a duplicate of bug 540810 and added the user to the CC of that latter bug.
Ah, the irony... *** This bug has been marked as a duplicate of bug 538783 ***