For me to remember someone's name perfectly, remember what collection of personality and phone manner attributes goes with the name, and also remember what collection of physical attributes goes with them, and remember all of this inside of the first month of their employment, says that something about them has made them particularly memorable.
There was one dude who was physically distinct enough to be not mixed up with anyone else of my acquaintance (large wide/tall, used cane, orange-haired), personality-tagged with "gamergeek; would hang out with outside of work", and because I tend to note people who have a "would hang out with outside of work" on my tags for them, I remembered his name. And then I noticed that there were two instances of that name on my list. One was from a temp agency with the temp agency code before the name, and one was not. One was marked absent, one was not. I caught the computer error pdq because I was set to flag on that name. It would ordinarily have taken me at least a week to catch that, if not longer. (I was in Field constantly at that point.) Right now I think I only know the people who have been there 6 months or more, because that's about how long I've been out of field. I know 2 new people: Silver Sunglasses Dude, and the Bathroom Cellphone Diva. Both of these are not for good reasons.
It's because of things like this that I totally go *omg facepalm* when I mention a name to someone who sees like 500 individuals a day or some crazy number like that (at an estimate) and the name gets the immediate response of "oh god them"...
...yeah, I'm staying at 30 foot pole distance from becoming more than involved in passing with an "oh god them" situation, and I'm rather hoping that I don't get to know their face, because that could get awkward. There's really no good way to un-know that someone is "oh god them".