It is possible to leave a Faction, if you believe that you will benefit somehow from being in a different one. The costs of doing this are steep, however.
If you still feel strongly about changing your faction, sell all of your Emblems, then speak to the NPC in your Faction House who shows you the bonuses for owning Emblems. Your Marks will be removed automatically, so best to spend them before hand.
Contributors to this page
librophagus - Main content
iSPANK - initial layout, minor edits, linking, tagging