Q:

What tag should be used for MMO questions?

What tag should be used for Massively Multiplayer Online Games?
Options that come to mind:
mmo
Most common? Combined with rpg for games that are both.
mmorpg
Also common. In contrast to tagging both mmo and rpg.
massively-multiplayer
More verbose suggestion. It has been pointed out that although recognisable and in the spirit of minimising abbreviations, it is technically incorrect - as one could have a massively-multiplayer game that was not online.

mmog
More correct. [Removed as the g is basically implied.]

A:

To me, having the tag be [massively-multiplayer] makes it too unwieldy.  As such, I was thinking something similar to Arda Xi's comment:

MMO for any massively multiplayer game
Second Genre-Specific Tag based on the genre of the game

So it would look something like this:

Planetside would have two tags: MMO and FPS
WoW would have two tags: MMO and RPG

This would allow people to find games in each of the sub-genres of MMO by searching for that genre's tag (i.e. Planetside is findable under FPS and WoW is findable under RPG). The search is easily configurable enough to allow someone to easily find MMORPGS by including [mmo] [rpg] in their search.  To me, the benefits overwhelm the costs.

A:

I would suggest using [mmorpg] for those games instead of the combination of [mmo] and [rpg] for  several reasons:

The genre is largest subgenre in both rpg and mmo, being even bigger than the rest of the genre in the latter case. (There are more active mmorpg players than non-rpg mmo players)
Giving a dedicated tag for mmorpg ensures both the [mmo] (non-rpg) tag, as well as the [rpg] (non-mmo) tag doesn't get flooded by mmorpg questions.
Remember, MMORPGs are an over $1 billion dollar industry! 1
Are we going to tag action-adventures with both [action] and [adventure]
It saves us a tag on those posts (we have a tag limit of 5)
we don't have an easy way to filter the non-mmo questions from the rpg questions (for newbies), while the [mmorpg] tag is easily found
MMORPGs have unique elements, not seen in other mmo or rpg games. (guilds doing quests)
searching for [mmo] [rpg] instead of [mmorpg] is counterintuitive for new users.
Actually, searching for mmo (non-tag) will find posts tagged [mmorpg], while searching for mmorpg (non-tag) will not find posts tagged [mmo] [rpg] 

BTW: didn't we agree to reserve the genre tags for the specific genres and not use them for the games, only for the genre questions.? (can't find meta-post now.)
(and for those saying MMORPG is not a proper name, wikipedia seems to disagree)

