I actually don't like the phrase "real life" when describing what happens in the physical world because it implies that the interactions we have in Azeroth aren't real. Captain Obvious says that WoW is not a single-player game. When we are playing Mass Effect, we don't affect anyone else if we get up to take a bio break or comfort a child. But in World of Warcraft, if we are in a group of any size, we affect others every time we AFK.
The phrase "real life is more important than WoW" is a mantra we hear all the time, and it is true in that you shouldn't shirk responsibilities in the physical world in order to play. However, if you have committed yourself for a period of time to other players, it is the same thing as committing yourself to any group of people in the physical world. Breaking that commitment falls under the same etiquette umbrella, whether in game or out.
Now, we can't anticipate all interruptions, and emergencies do trump the inconvenience of your online friends. (Captain Obvious points out that the same situations happen in the physical world as well. He's rather annoying that way.) But most of the time, we can avoid or limit our unplanned AFKs with proper scheduling and preparation. Lisa and I tackled this subject recently and have also tackled it in the past. All players have to handle interruptions, but we don't all handle them the same way.
The Spawn is now old enough so that any call-outs from the bedroom can wait a few minutes until The Spousal Unit or I are in a good place to AFK. But when she was much younger and needed to be dealt with quickly, I tended to solo pretty much exclusively. Even now, I usually decline group activities when she is awake and perfectly entertained just so that I can drop everything in case she needs me. I am probably being overly cautious, however. The Spawn is a fellow gamer and treats us like she wants to be treated most of the time. If she's in the middle of a tricky part in Skylanders, she doesn't want to be interrupted, either.
How do you deal with interruptions in the physical world while you are playing? Do you think that AFKing with no warning is OK for certain situations other than dire emergencies? Are you more considerate with guildies than you are in PUGs when you have to leave the computer? (Note: I'm asking about PUGs that aren't funsuckers, of course.) And if you are a caregiver, how do you deal with your playtime?