Flametongue Totem is a Fire totem, and thus cannot be used at the same time as another fire totem. Like all shaman totems it only has 5 hit points and is easily targeted and destroyed. When used in a raid group it will affect everyone in the raid who is in range.
Its effect is inferior to Totem of Wrath, and doesn't stack with it. Hence, if another Shaman in your group uses Totem of Wrath, there is no use dropping this totem.
Some abilities, like Healing Stream Totem and Earth Shield, have long durations and use the caster's spell power at the time of casting. By placing a Flametongue Totem before using such an ability, it effectively gains the bonus from the Flametongue Totem for the whole duration, while allowing the caster to move out of range or to use a different fire totem. This can be especially effective when used to boost Earth Shield before a fight in PvP.
/Patch 3.0.2 (14-Oct-2008): Totem functionality completely reworked. Now grants spell power instead of causing melee attacks to deal fire damage. Totem duration increased from 2 to 5 minutes. Totem made raid wide.
Patch 1.11.0 (20-Jun-2006): Totem duration increased to 2 minutes.