Seems like every game becomes a snowball and it's not even always my fault. They are winning in lane, so they get more last hits. They get more last hits, so they continue to win in lane. Just played a game where my support nearly died before first wave (no idea why she was up so far), so I couldn't even safely last hit first wave. The entire game, the enemy carry, a Twinblast mirror, was up 10-40 CS and there was nothing I could do except focus on farm and try to warn my mid (who wasn't warding, it seemed).
But it's not just team diff. I was in solo and we traded even until the Crunch got omnivamp. He started winning every trade and zoned me off farm (I'd take 50% HP just for getting close to him). Obviously, this led to him being unstoppable and me being very far behind. The obvious thing is to try and catch up on farm while the enemy laner rotates, but that doesn't work if the enemy laner ignores the rest of the map just to zone you, or if they're rotations are effective in securing kills and objectives. I could counter-rotate, but then I might have to fight the guy who's been kicking my ass all game or just do my best to support my team, leading to gaining no farm and still being just as far behind.