When talking to somebody face to face, you usually do have and can claim the majority of the other person's attention. While exchanging instant messages, you may have the immediate attention only intermittently.
When instant-messaging with somebody,
- you do not always have the other person's full attention,
- cannot readily claim it and
- should not expect it.
The physically near usually takes precedence over the physically remote. If you are approaching somebody chatting on the computer, you'll want them to turn their attention towards you, at least for some time. Now, if you're at the other end of the instant messaging chat window,
- do not be alarmed if the other person suddenly stops responding,
even if they do not announce or explain it beforehand. Chances are it's not a rejection of you as a person but rather a response to the call of immediate and more urgently felt needs. The problem is in the medium — or in the lack of a medium: you cannot see or know the reason for your pal's irresponsiveness. It's best to accept it without and before understanding it.

