Here's some info on the origins of the 'Alignment' 'meme'. It should probably be renamed Alignment-based Demotivational Posters if you want accuracy, unless you want to create a super-entry for it, since it is technically a subset of the RPG Motivational Poster genre. Your call, though. I just thought I'd be helpful.
Oh… I think I hear some tl;dr coming…
The alignment discussion/'meme' technically first sprouted after the release of AD&D back in '77. Yes, THAT far. AD&D was the first to introduce a second axis to the original linear Lawful → Chaotic alignment graph, bringing the total from 3 to 9.
TSR spent the next couple of editions refining the points before settling on the standard we all know – and during this time, players experimented and became fairly enamored with the concept; especially those at polar ends of the spectrum. So much so, in fact, that certain players would abandon logical story decisions for the sake of remaining in the extremities of their alignment. (Clerics refusing to kill anything, evil characters that would spend the game firebombing kittens instead of the objectives, etc.)
This exposed the inconsistencies in the system – that while law and chaos were easy to discern, good and evil tends to depend a lot on one's point of view, and often, the player's definition differed from that of the DM.
Subsequently, jokes began to rise that added a third, subjective axis to the 'improved' duilinear system, turning the graph into a cube. You'll still hear some comment derogatoritively about 'lawful stupid', or 'chaotic awesome', etc., when talking about certain characters/methods of roleplaying.
RPG.net user 'ThomasT' is credited for bringing RPG's and motivational posters together on 5/19/06.
http://wiki.rpg.net/images/0/0a/MPost1-Cthulhu.jpg
Although vague, this format was open to a lot of interpretation, and it flourished as people began using it as a teaching/evaluative/snarkasm tool.
The original RPG.net motivational posters thread has undergone several renewals since – the first thread alone needed to be closed after the forum itself began to grind to a halt due to overwhelming numbers of visitors; by then there had been 37,400 posts, and it contained an estimate of 22,000 posters.
Since then, the trend shows little signs of stopping, especially after the fan-polarizing release of the 4.0 rule system.
Anyways, that's my 0.00002 bits on the subject.
Feel free to ignore it if it's more info than you need, or correct/delete it if it bugs.
(Since you guys like sources, here are some.
http://wiki.rpg.net/index.php/Motivational_Posters:Main_Page
http://community.wizards.com/go/thread/view/75882/21016557/The_alignment_system_for_DND_4th_edition?pg=1
Myself, my husband, and my friends, who have been playing d&d since before the A was added. _)