A single serving friend is someone who is your friend for a short time, then you never see them again. For examle, when you sit next to someone on an airplane and you talk with them. You have two or three (or more) hours together, then you never see them again. (Unless you're my parents. They met on an air plane.)
But that type of single serving friend is easy to deal with. You probably never see them again. What about the guy who fixed your computer at work though? He comes by, fixes your computer. As he's looking at it, you get to chatting. Next thing you know you see him later on in the day and you say "hi" as you walk by.
But how long does it go on for? 6 months? That seems a little long, doesn't it? So, how does one handle this delicate situation?
During the summer my computer at work was screwed up so I called the help desk. They had to send someone. That someone came, let's call him Fred. He had to come a few times to fix my computer. After a few times he ended up just taking my computer away and re-imaging it. I work in a pretty large complex; he works one floor below me. So I found myself seeing him in the halls, and on the elevators and saying "hi" to him.
But it's conceivable that I will never deal with him again in a tech-support capacity. So, how long do I have to say "hi"?
Just a day or two after I had decided to stop saying "hi" to him.....well remember the phone I found on the way to work? Yeah, well it was his phone. So, now I'm back to saying "hi" to him.
Now, I do want to stay on his good side. He's a nice person, and he can severly screw up my computer if he so desired.
Does Emily Post's famous etiquette have a chapter on single serving friends?