I have trouble remembering names. I'm fairly good with recognizing faces, but stink with names. Nonetheless, it's hard to imagine being unable to recognize familiar faces. However, folks who have an impaired ability to recognize faces suffer from a condition known as "prosopagnosia" or "face blindness."
This could be a condition that develops later in life, or is something a person is born with, but it can wreak havoc with social interaction. Can you imagine going through carpool line and not knowing which kid is yours until you heard her voice?
Similarly, there's a condition called "phonagnosia" or "voice blindness," which leaves an individual unable to recognize voices. Scientists say that we can usually recognize a familiar voice over the phone with just one word, but those suffering from phonognosia can't even recognize the voices of parents or spouses.
So, the bottom line -- we shouldn't be upset if someone doesn't immediately recognize our voices or faces because he or she might be suffering from prosopagnosia or phonagnosia.
Now, if only I could get spellcheck to recognize my name as a real name. I don't think it has any good explanations for its continuing failure . . .