I learn names very quickly. I usually know the names of half of my students by the end of the first class session, and I'm typically at 100% by the third session. The flip side of this, though, is that as soon as the semester is over my brain purges itself of that information. I'll be walking across campus and run into a smart, participatory student whom I had in class just two months earlier. . . and I'll have no idea what her name is. I'll remember her, of course--which class she was in and where she sat, and even all kinds of extraneous information like the fact that she's on the student paper, or she lives with her sister, or she just moved here from South Dakota. But her name? It might take me ten minutes of hard thinking, and long after we've parted, to recollect.
This is, surely, an inevitable consequence of teaching more than a hundred students a year, year after year, and some of my students actually seem to expect to be forgotten--I've had "A" students email me the semester after taking a class with me and open their request for a recommendation by saying, "I don't know if you'll remember me. . ."
Still, it bothers me not to have better recall, in part because I tend to have a good memory for detail, and in part because I've always assumed that anyone I've had any kind of meaningful encounter with will remember me: I once emailed a former TA to ask for a recommendation letter, three and a half years after I'd taken his section, and it didn't even occur to me to remind him of who I was; I just launched right into a chatty message updating him on my life and explaining why I thought he'd be a good recommender. Now, it's true that I'd done very well in his class, and it's also true that, being an INRU grad student, he probably hadn't taught more than 80 or 100 students in his entire graduate career--but it's not as if I'd participated much in section, and we certainly hadn't had anything like a personal relationship.
Maybe that's a sign of how cluelessly self-important I am, or maybe it's an indication of the difference between my educational experience and that of many of my students: if you're a first-generation college student, or a transfer student, or someone who hasn't been continually petted and praised by your teachers in the past, you probably tend to regard the distance between yourself and your professors as that much greater. For that matter, if most of your classes average closer to 30 students than to 15, it might be reasonable to assume that your professors see you as no more than another line in their gradebooks.
Still--aren't we all disappointed when people forget our names? I take it very personally when someone fails to remember my name, especially after multiple introductions, and I can't help but see it as either a moral failing on that person's part--so uninterested in other people! So absent-minded!--or as evidence of my own inconsequence. It's that latter possibility, probably, that most upsets me, and I'm sure that my students feel similarly even if some of them are already half-prepared to be forgotten.
So I try to learn names quickly, to pronounce them correctly, and to use preferred nicknames when applicable. This doesn't mean that I know my students in any profound sense--or that I know most of them, really, at all--but I guess that I see it as a way of acknowledging and validating their identities in some fundamental way.
That's probably why I hate how quickly I forget their names, too: if I can't remember even that one, basic thing about my students, maybe they were just lines in my gradebook after all.