Before Twitter/Facebook/Google+, your instant messenger status had to not just tell people whether or not you were free to chat, but serve as a rudimentary thought dump of quotes and witty sayings. Now social networks actually exist, your status can finally just be your status. But even then, what are the dos and don'ts of IM status?
What might not be obvious is that while you use your IM status in one way, it might not come off the same way to others. Here are some major use cases of IM status and how it's perceived.
The person that's signed on and available all the time
Why you use it: You leave your computer on all the time - either for torrenting, or just so you don't have to wait for it to boot and launch all your apps again every few hours. As a result, you leave your IM logged in because you want people to be able to reach you and leave messages that you can check while you get back to your machine. Like voicemail, you may not get to their IMs immediately, but you will eventually.
How it comes off to other people: The difference between IM and email is the immediacy that goes with being signed on. There's an expectation that when someone is online, they're at the computer, or at least in the vicinity, occasionally checking in.
If you leave your client signed in all the time, it puts a heavy burden on your status. You should be vigilant with your Available/BRB/Away statuses so people know what to expect when they IM you. If not, every instant message is like a game of craps. Craps. (You're being crappy.)
Verdict: It's not that horrible, on a grand scale, especially if people have gotten used to seeing you on all the time, and know more or less what your hours are for being in front of the computer. It becomes annoying in an urgent situation where someone wants to get ahold of you, because they need to wait a few minutes after IMing you to see if you'll respond before they move on to something more immediate like texting or calling.
The person that's away all the time
Why you use it: You want to be available, but you don't want to be seen as available. You want to convey that you need to IM for work, but don't really have time for idle chit-chat throughout the day.
Another possibility is that you're online via your smartphone, and want to be reachable, but don't reasonably have the chance to check your phone all the time.
How it comes off to other people: Setting your status to constant away pretty much negates the status altogether. Doing this is the same as being Available all the time, and your status becomes meaningless. Many people do this, and most of us learn to ignore their Away status entirely.
Verdict: It's a minor infraction if people are used to IMing you regularly, but for new contacts it might be confusing at first. Are you actually there? Do you not want to be bothered? Such questions might need clearing up.
For mobile phone users, you should clearly mark your away status as "on the phone" or something similar. This way people will know not to expect an immediate response from you, but they know that you can be reached.
The person that has their idle turned off
Why you use it: Turning off idle detection is a similar tactic to always being available or always being away. You don't want people to know when you come and go so that you won't be bombarded with messages when you return from lunch.
How it comes off to other people: Along with the status, a person's idle is vital information to determine whether or not they're in front of the computer. Leaving this on lets people know exactly when you've come back from lunch, or a meeting, or the bathroom. It's even beneficial for YOU, because you can use it to temper people's expectations on when you're able and not able to respond immediately.
Verdict: Turning off idle detection becomes another veil to mask whether or not you're actually at the computer. If you're aiming to be more considerate, you should enable idling so people know when to expect an immediate response or not.
The person that's always invisible
Why you use it: You might be hiding from someone, or you might be hopping on quickly to check if a contact is online, and you want to stay invisible because you don't want to get drawn into a long conversation about the Captain America movie.
How it comes off to other people: This is the worst. If you're invisible, you're essentially saying that IM isn't for other people contacting you, it's only for you to contact other people. It's just like someone who has a mobile phone that they never answer, justifying it as a convenience for them only. Unless you have a good reason to be invisible, like if you're hiding temporarily from someone who wants to find you, it's a selfish thing to do.
Verdict: Used very sparingly, being invisible isn't a horrible thing. What becomes unforgivable is if you're always using invisible as your default status and messaging people that way. IMing then becomes a one-way activity, where you're only reachable when you feel like it.
The optimal use of your status
Although impractical, the perfect use of IM status would involve always setting your status to reflect whether you're at the computer and whether you can respond immediately. Leaving your idle counter on and using the invisible status sparingly is also important.
And if you want to be very vigilant, make sure to sign out when you're going to be gone, and sign in when you're back. Just think about how you would want others to use their IM status, and apply it to yourself.
Etiquette is, by its very nature, subjective. What's acceptable today probably wasn't acceptable 20 years ago, and what's unthought of right now might be commonplace in a decade. It might also be seen as pedantic to some, because if you boil it down, it's just an arbitrary set of rules that we all abide by to make all our lives easier. So weigh in and tell us what you think about this subject. It's one of the few times that just about everybody's opinion is more or less as valid as everybody else's.