At least for me, since I have very little of it.
Today I went to a meeting with a prospective client, and we were talking with two people, one guy, apparently manager of the company, and a girl, in charge of the security area.
Blah, blah, yes, I teach for peanuts, no, no, more peanuts, and so on, then she tells me, she knows me from somewhere.
La Plata... CACIC?
Ok, she had been, in 1996 or 1997, in the audience for a lecture I gave on hierarchical proxying, in a congress called CACIC, in La Plata.
She even remembered I was at the Universidad Nacional del Litoral at the time.
I just remember that I did give that lecture at that time, and that it didn't work out very well (I redid it the previous night because I lost my notes, it was a mess).
How the hell can she remember that? I have no idea.