1. The job is no longer challenging, you get bored, so you stop working as hard, thus underperforming.
2. You are associated with a failed project.
3. A previous action has created a perception of you. This can be:
a. emotional outbursts (the example used is a person being too fragile because of emotional distress during a divorce).
b. you are seen as a gossip
c. you were caught trying to advance yourself while hurting someone else.
4. You become fed-up with the game, the bureaucracy, whatever, and stop trying.
5. Change in manager changes your job description into something away from your strengths
I am sure there are more. The difficult thing in all these cases is realizing that your current situation is simply spinning your wheels. Bosses will not spend political or physical capital for people in these situations, and fighting the perception(s) can become an uphill if not losing battle. In the long run, you will be better off following lesson 2 from the post on Monday. Move on! You will escape the perceptions (even if you have to take a step down from your current position), reinvigorate your personality because you will be doing something different, and improve your career trajectory in the process. Don't let the fear of change stop you. Embrace it!