My last game, a spamliner deliberately glutted every single one of my routes, turning what was a modest postive cashflow into a disaster-level loss. I was flying 717's, he flew 747-400D's on puddle-jumper routes!
Who does that? I have an idea, but I won't say the name here.
That just isn't fun, and that's what I'm here for. Until it gets fixed (in at least a few worlds where spamlining is banned), I'm out of the game.