I had a very interesting story to tell about a negative identity column from my recent Comprehensive Database Performance Health Check.
Recently I had the opportunity to work on a project where my client had a negative identity column. The column was continuously decreasing. It starts at zero (0) but keeps on decreasing. When I asked them why the column is negative, they were really not sure about the reason. After carefully looking at their deployment code they figured out that they had accidentally put -1 as interval instead of +1 and that was the reason for the decrementing identity