to go back on that slightly, no one is completely useless. you'll always need people to cut your hair and mow lawns and make useless radio programs to listen to while you get on with real work.
trouble is, these people are rarely interesting.
so to get some definitions sorted out let's say
now you could say that this was a selfish definition since I'm basically saying that a person's usefulness is directly related to my interest in him/her....

hmmmm....and I care because ???

(note - if you meet your mates in pubs, don't bother to read on)

me and my best friend came up with a theory a long time ago only to have it rocked to the very core by a throwaway statement from my mother.
well it survived and here we go. (first and last time in writing)

this is in a childish tone - but since it is a child's prerogative to utter truths
no one else will speak (paraphrasing Neil Gaiman slightly) - I'll let it stand.

that's it. (that's ha)

told you it was childish.

i can quote Harlan Ellison this time, from the introduction to Mr. Gaiman's 'Season of Mists' Excellence in the untalented and ordinary produces pleasure and awe while in the minimally talented it produces hatred and envy.

ha. i'm on a roll now so I'll add in the final bit which is all just a rework of the same thing
(you can see we have far too much time on our hands...)
the way i see it confidence splits into two types...
if you're not sure which you are you're group (a)...
if you're group (b) welcome to the club.
(which one day I will actually get around to setting up - takes so long to find cool people otherwise)

be the latter. eat the former. later.