Posted Mon, Jan 23, 2012 by Martuk
Players will still have the option to take missions from any of the three factions, but they’ll only belong to one, which will control their access to PvP objectives, merchants, missions and faction channels. You can still change factions if you want, but it’s not meant to be a simple process.
Additionally, Faction Friendly Fire will be eliminated with the exception of Clan Wars, Bloodsports and dueling.
Source: Fallen Earth Developer Blog