Why do I have trouble remembering faces?
Having a poor memory when it comes to faces is not uncommon. After all, we meet so many people during our lives that not being able to remember some of them is completely normal. In fact, the ability to remember and recognize facial features depends on one's age. Ages 30 - 34 are best at this.
Face blindness however is different. It is a disorder known as prosopagnosia, where you not only fail to remember faces, but your brain simply can't recognize other people at all.
So people who suffer from this disorder learn to recognize people by other means, such as hairdo, voice, accessories, etc. If you change one of these parameters, a prosopagnosic won't recognize you.
How can you tell if you have prosopagnosia?
If you usually describe people with words that don't relate facial features (example, "a woman in glass"), or if you avoid names when communicating with people, then it's possible that you suffer from face blindness.