From SA Mafia Wiki
The LumpenList™ is a terrible scumhunting tool that is comprised of a list of all living players, ranked by descending order of scumminess and divided into 4 tiers. The criteria for ranking and for tiering is up to the listmaker. Commentary text is encouraged but not required. It is named after the only person who thinks it's actually worth using.
The goal of the practice is to help the listmaker organize and concisely express a snapshot of their thinking, and also lose the game. It requires carefully taking the entirety of the set of posts, weighing the interactions between every member of the game, and fitting it into a framework that matches a likely hypothesis about the setup. By being required to fit every player, it forces the listmaker to reread people and consider things that otherwise might have been skimmed over, while still making baseless assumptions about the setup that act as confirmation bias. It also gives the benefit of openly advertising the summation of a player's suspicions and possible biases in an explicit and concise way that can be easily referred to by other players, including the scum to allow them to nightkill only the towniest players.
The LumpenList™ Doctrine® holds that if EVERY player would make a list in this format (at least each game day), powerful inferences could be made and contradictions detected that would expose the scum; unfortunately town players often don't have opinions about the vast majority of other players, and forcing them into an opinion can lead them to contradict earlier opinions since they were not genuine.
Nobody was going to run a game forcing players to post Lumpenlists because of frequent dismissals that the idea would be "stupid" or "worthless" (by everyone). But science marches on. In Feb. 2009, Lumpen ran the power-role-less Instant Runoff Mini Mafia to test this hypothesis, and the town players lost despite (or perhaps because of) the forced listmaking. The idea is really stupid and nobody worth a shit would think it would work anyway.
This has not deterred Lumpen from advocating it unironically in every game he plays.