I was under the impression that the purpose of a guild is to have a group of folks that you enjoy playing with and have common goals. It's a good way to share the game with friends and family, in addition to experiencing new adventures and progressing together. Triamala of Blackwater Raiders fears that such actions are seen as cliquish, causing drama amongst the ranks.
In a post in the Guild Relations forum she said that a previous guild of hers feel apart because of cliques and her current guild is facing the same fate. Members of her guild apparently get up in arms if she runs instances together with her husband or other friends. In a later post she admits that she is closer to the officers than other guild members because they've been playing together for quite some time.
A number of the responders have had similar experiences. Problems truly occur when all others in the guild are ignored except during raid times. Chlover of Hyjal believes that there is no harm in playing with friends and family:
My main is a healer, my brother a tank, my sis-in-law a mage and hubby an enh shammy. About 1 to 2 times a week we agree on a heroic daily and spam guild looking for a 5th. What harm does this cause the guild? Does it make a difference that I'm an officer? I heal for other guild 5 man groups without family 1 to 2 times a week as well. I am on a 10man ZA team without family. Frankly its more fun to play a 1 hr heroic magT with my clique than to help a group of guild alts get a drop they want from Botanica..
I would probably reconsider my guild choices if I were in Triamala's position. My play time with my significant other is as important to me as my play time without him. After all, I never would have gotten started without him. It comes down to my theory that when it stops being fun, it's time to do something else