Different words have slightly diffent meanings and I would like to begin a discussion about common MMO words that might not translate into the Fallout Universe.
Like a GUILD is an association of of trade craftsman, such as a the Slaver's Guild whose trade is Slavery or Thieve's Guild trade is Stealing. The Guild acts as both a learning institution with the Apprentice system, and as a certifier insuring quality control over the trade. However in MMO's guild and CLANS are often a broad label applied to any association of Players. A CLAN is actually a group of people joined by Familial bond (keeping it in the Family) or a percieved Kinship (All ghouls are share the bond of radiation). Corporations have a legal identity that is sepate and different than its members, and in a way is a far more acurate term for MMO "Guilds, but it lacks the flavor of the wasteland. The term I am favoring for the Wastelands is GANG, "a group of three or more people who, through the organization, formation, and establishment of an assemblage, share a comman image. Usually affiliated with criminal activity but has its origin with Old Norse gangr meaning "a group of men". The reason I like gang is because you can keep the acronym LFG, but now meaning looking for Gang.
Of course what about Groups, Squads, Teams and various other titles.