What you describe is the intended, valid use of the metric. What I am complaining about is people who care on a personal level about what their own karma is, and who do things just to inflate that number. Facebook/Myspace "friends" whom you don't actually know? "Vote up if *" posts? Lolcat or comic or whatever posts? I know HN is (mostly) blissfully free of these things, but they are a direct consequence of the karma system.