I don't know that it does make a difference particularly. I mean, unless you correspond with them or actually have a situation where you run into them down the road, how would you know anyway? I run into old students constantly, MOST I don't remember by name because over the past 30 years I've probably taught over 6,000 students. They don't seem at all fussed about the fact that I don't remember them; rather, they usual approach me with "Mrs. A, you probably don't remember me, but my name is _____ and you taught me in 7th grade . . ." I'm not at all embarrassed that I don't remember them and they aren't upset about it either. On the other hand, there are a few students who over the years really stuck in my memory, and I even correspond with several of them via Facebook, etc., but it is a much, much smaller number.