When it comes to communicating, a lot of people I know seem to prefer the most convenient method of communication that's available, usually text messages or e-mail, and if that's not available then chatting online. If that also fails then maybe a phone call, and in the worst case a face to face meeting is unavoidable. I'm all for efficiency, but I sometimes hate talking to people online because of the lack of information available, and the risk of misunderstandings.
Especially chatting and short text messages are horrible. The usage of smileys seems to be a cultural thing. A message full of smilies from a Japanese girl might mean that she's dumping you, while a completely undecorated message from some foreigner that looks like an insult might actually be meant in a funny way. It's hard to guess the true meaning, especially if you don't know the person, or haven't spoken to him/her face to face in a while. Fortunately there is a smiley etiquette that most people I know follow, and usually when somebody says something that could in any way be interpreted as insulting, it will be followed by ':)' or a ':P'. I use this a lot with friends who lack the sense of sarcasm, which can completely twist around an entire conversation if I'm not careful.
I very much prefer face to face conversations, especially with people who I know, but don't yet know well enough to guess what they mean just based on text. Important conversations or decisions too absolutely have to be done face to face in my opinion. There's just so much subtle information in a person's face and body language, and you can only pick that up if you can see the person you're talking to. Webcam is not good either, cause it doesn't convey the same amount of information, and the environments of the two people talking can be completely different. Having access to all this information is like a sixth sense that I think a lot of people are forgetting about. A single look, a moment's hesitation, a slightly different tone of voice. Pick up on these things and you can form a better mental image of the person you are talking to and the situation of that person. You'll be able to understand better how he/she feels, and you'll be able to predict what he/she is going to say. It's a valuable source of information that should not be forgotten in this age of text-messaging.
So please, people, stop twittering. For pete's sake.