Since I feel bad about hijacking your other thread, let me respond to your article. It's important to remember that in Diplomacy, two-power wars tend to hurt both participants. If you haven't seen it, I recommend reading about some of the research into Prisoner's Dilemma games (and some of the n-player extensions). [Quick summary: cooperative play is good, surprisingly good if you haven't seen the problem before]
For what it's worth, I find myself very rarely lying when playing, and even more so when I am playing well. Rather, my best play is characterized by successfully understanding the view the other six players have of Europe, and using that understanding to create conditions where they will, for their own reasons, choose to do things that benefit me. This doesn't mean that I nibble away at each of my neighbors; for some reason, my neighbors tend to get upset when I do that, and I'd rather have one enemy that borders me than three. You do have to end up having enemies in this game as part of making progress, although if conditions change, those enemies might later become allies. But, in a really successful game, the other players' worldviews are such that they consider themselves better off if I win my wars (even as I'm growing), or at the very least not worse off to the point that they should intervene.
So, yes, keeping friendly relations with as many people as possible is always good, and worth doing with your enemies, too. Don't stop talking to somebody just because you're at war at the moment. But also don't nibble -- if everything goes perfectly, nibbling can work, but it rarely does, so if you have found a profitable alliance and a winning war, keep it going, just try to make sure that your side of the war goes a little better than your friends'.