"The 'nade spamming' meme was the perfect storm of unfortunate circumstances," writes consultant Nils Pihl, in a new feature which gets to the heart of precisely how players ruin games for themselves.

In Call of Duty: Modern Warfare, there was a critical flaw in Crossfire, one of the game's maps. Players could lob grenades over a wall at the start of the match, scoring instant kills.

Once this idea was found, it replicated -- and couldn't be stamped out, writes consultant Nils Pihl.

"There was a good statistical likelihood that an enemy would be on the other side, and chance would determine if you got a 'free' point or not. The combination of predetermined starting points and insufficient obstacles between the teams had allowed one creative player to get a stylish kill."

"The problem was that the meme was easy to copy, without requiring any particular skill at all," Pihl writes.

"Random interval reward schedules can be incredibly addictive. The fact that you didn't know if you would hit an enemy or not turned throwing the grenade into highly addictive gambling scenario. All you had to wager was a cheap grenade, and you could win very desirable points in exchange. It was a meme that was easy to copy because it was so easy to observe and understand the required actions, it was fairly successful at a low cost, and it was very addictive."

In his feature, Pihl goes into great depth about exactly how and why the players ruined the game for themselves, and writes about how game rules have unintended consequences.

He also contrasts Modern Warfare's problem against how Blizzard tunes StarCraft II to mitigate dominant strategies. He describes the cycle of discovery of memes -- and the imposition of new rules by players -- on multiplayer games. You can read it now on Gamasutra.