My family would know I was missing. Which, after everyone found out, would be quite a large number. However, they wouldn't really know, "who", was gone, just that something they are emotionally attached is gone. If I was dead or never found it would be a tragedy for them, and their lives would be easier once they got over it. It's up for debate whether any of my friends would ever find out. Quite a large possibility they would just be wondering what ever happened to me and would never really get a clear answer.
I suppose I should be grateful for having such a loving family, but would you care that much about how your co-worker felt if she always called you Bob when your name was Bill? lol. If I were to die, everything I ever valued in this life would most likely find it's way to some sort of Spanish inquisition type book burning. Now that I really think about it, It may very much be that if I were to go missing and never found or died, it would be as if I never existed, to my family, anyway, the ones who would notice me gone. They are good people, though. I've been rather hard on them a fair portion of my life...