This fairly old, but interesting, article from
Nick Yee's Daedalus project gives an insight into one of the "uberguilds", guilds that persist across games
and aim for the top. As the first to kill Ragnaros on their server, Talon's guild is a marvel of military organisation,
but not without criticism--the guild leader prefers not to let women in the guild, for example.
Talon's rules for membership are especially clear: you need to be able to take criticism, have good attendance for events, and have the "guild comes first" attitude. Many of us have just joined guilds that were openly recruiting, that had friends in, or that a party member invited us into because they liked our style--this is very different territory.