Well here's the really interesting thing about the position I posted: Black actually is a computer - Deep Junior.
Garry Kasparov is playing white - this is from a 2003 Man vs. Machine match he played against Deep Junior. You can see the full game here: http://www.chessgames.com/perl/chessgame?gid=1260051
So, this has made me think about a few things that might be a pertinent tangent for this thread to head - Why of all things would IBM program a chess computer to calculate resignations? If you think about it - refusing to resign, and playing on right to the bitter end would favor machines... they never tire, simply calculate. I actually think that the correct answer will shine light on the question we've been discussing.
Oh - and I wouldn't never "seen" that Black's position is resignable... I'll likely never be that good. In fact, just so everyone in this thread knows, I'm way too prone to resigning early (under 10 moves sometimes if I panic)... so I really have to conceede that I'm not trying to come off as a resignation expert or something silly like that. It's just an interesting question.
So: when to resign? The computer Deep Thought chose to resign right there.
An interesting comment on the thread beneath the game I posted:
RonB52734: I've looked today at two GM vs. Computer games in this opening (today's opening of the day) -- this game and Shabalov vs Mephisto, 1992, 1992. Both ended with the computer resigning. I ask myself: "Self, what motivates a computer to resign?" It looks to me in the present game like Kasparov's rook on the 7th rank probably pushed some "positional value" formula up a notch to a point where the computer figured it was down a bit more than the equivalent of one piece. (down 2 points for the exchange, opponent's rook on 7th, my knight hanging on the edge of the board). In the Shabalov game, Shaba's advantage is a full piece just in material, plus he has a protected passed pawn and a rook on the 7th (but on a wide open board), but it is less clear to me what triggered the computer to resign there.
The point is that as far as I understood this site policy, the main way of playing here is having one to three days to play each move, so if internet connection is expensive for you, the best advice I could give you is to have daily sessions were you play moves in all of your games where it is your turn and then connect the day after.
When you disconnect your games are not over.
If you have a so huge advantage, you will win the game in a few moves anyway.
I think it is fair to resign when you know you will loose but on the other hand i also think it is misplaced to ask someone to resign.