Wogomite - it is my conclusion after many years of play, that sometimes the game is won before it starts. I see it more in Quick Game here, but you get an awful lot of bronze players who play that and when they come up against me they make comments before the game even begins like "wow, nice rank, you must be real good!" and stuff. When I see that, I know they aren't going to win - its already in their heads that they've drawn an impossibly good player. You cannot underestimate the mental aspect of this game and the need to apply your focus - but if you're already thinking you're outclassed because the opponent has a much better ranking than you, the chances are you won't give the focus 100% so your slim chances of winning now become even slimmer.
Seen it happen in the full game too, more so on other sites where you can play all levels of ability. It used to happen to me too when I was at the equivalent of a gold player. I'd see a top player and think to myself 'oh great, a loss coming up' which isn't the right approach. I found myself starting to beat these players more consistently by accepting the challenge and applying myself to the game fully.
On the flipside, and I'm guilty of this myself sometimes - the opposite can apply. As a higher level player, I see a bronze player with a record of say, 60-140. I take my eye off the ball thinking 'easy win here' and make some moves you wouldn't dream of making against a better player. But if the wheels come off then all of a sudden you can lose and you're left a bit shocked but with only yourself to blame!