It's been a busy week at Player Vs Developer productions, which has been holding up this post for a few days now. Despite the late arrival, I'd like to get back to discussion of the Children's Week Achievements because there's an interesting incentive design question at hand.
Euripedes seconds the complaints made by Scott Jennings - that the PVP achievement for the holiday encourages individual players to pursue selfish activities in a group battleground, thereby screwing over players who actually want to fight battles instead of work on holiday achievements.
Why are PVP incentives constantly causing so many problems in games?
Absolute versus Relative Merit
Players who are attempting to tackle group PVE content, such as raids, have to meet an absolute progress standard. The raid must be able to deal X damage before everyone dies. There are ways of reaching that goal - increasing the raid's DPS so that the boss dies faster, or learning to avoid attacks so that the raid takes less damage and lives longer - but victory or defeat is ultimately an absolute question. Either the raid got the job done or they did not, and the value of their victory depends on how hard the boss was to kill.
By contrast, the value of a victory in PVP depends entirely on the quality of your opponents. Blizzard can try to generate better match-making algorithms (and apparently failed at that task yet again for the current arena season), but there is much less of an absolute standard. A poorly rated team might beat a much better opponent because of a favorable matchup, or an untimely disconnect.
This distinction gives rise to a second difference between PVP and PVE rewards.
Incremental progress versus all or nothing
That PVE raid encounter is all or nothing. Either you beat the boss, or you did not. Perhaps you learned something from the loss that will help you win the next time, but there is no explicit, in-game incentive for trying and failing.
Unfortunately, when players fight other players, half of the players are going to lose. As a result, developers HAVE to include some rewards to compensate the LOSING players for their time if they want to attract a large chunk of their players into PVP. If there is no reward for failure, the worst players will never win, never get rewards, and therefore quit playing. Then there will be no one that the second worst tier of players can beat, so they will cease to be able to win and earn rewards, and they too will quit. In the end, there can be only one.
(This might sound like a good deal if you think you can be that last one standing, until you realize that the resources your developer can afford to spend improving your experience are going to be cut drastically if no one else is using the content.)
Sharing one goal
As a result of the first two points, there is relatively little incentive for an individual member of a raid to act against the raid's best interest in pursuit of a selfish achievement. If the raid wipes because someone was tanking with no pants, EVERYONE misses out on loot. Sometimes the entire raid might decide to behave sub-optimally in pursuit of an optional achievement (e.g. sitting several raiders outside the zone to get credit for beating the bosses with a non-full raid), but, in the end, the boss still has to die or no one gets anything.
By contrast, your PUG battleground group is full of players who have differing goals. Some players are chasing achievements and don't care if the team wins or loses (and, in fact, may prefer to sabotage their own team by failing to defend flags so they can get more chances to recapture them). Meanwhile, by putting a value on failure, the devs invite each and every player to make their own personal game theory decision on when to give up. All of which is a disaster if you were actually there because you wanted to fight and win the match. This is NOT a new problem for Children's Week, the achievements merely make the issue more obvious.
Your timesink or your game
In the end, this is one of those places where the developers face a conflict between the quality of their game and its ability to occupy players' time. The Children's Week achievement had to be what it was, rather than a requirement for helping players' sides to victory in the actually battleground match, because otherwise players would have attempted to claim the required victories while AFK.
In a perfect world, there's enough new content to keep players entertained so that you don't have to try and bribe them into grinding battleground content that they don't want to be doing. The issue is that Blizzard doesn't have the capacity to create enough other content (nor, in fairness, does anyone else). Not only that, they especially cannot afford to spend precious time developing content that some of their players will not use (/gasp).
As a result, they MUST try and lure non-PVP players into PVP (with selfish personal incentives), they MUST try and lure raiders into solo daily quests (with money to pay repair bills and cosmetic rewards), etc. And so, instead of rewarding the one part of PVP that actually matters - who got the win or the loss - we get selfish and detrimental incentives. A true PVP meritocracy, no matter how well it functions, simply will not be enough to convince players to continue reusing battleground content from 2005 on a regular basis.
And now, if Tom Chilton is to be believed, we get a new battleground in patch 3.2 with all of the same incentive holes that are attached to the five current ones.
Too bad that player created content thing didn't work out, because the problem is, as it always has been, that Content Is King and there just isn't enough content.