Actually, I'd prefer that coworkers don't start blowing up my phone/PC with chat alert beeps for an extended question until they've confirmed that I'm not in a meeting/trying to concentrate/etc.
I've started using the "Do not disturb" option in my Office Communicator when am in important meetings. Using that option on the communicator makes it impossible for someone to send me a message. Any attempts explicitly fail on the sender's end with an error stating the obvious - The receiver has set "Do not Disturb"
I have seen the embarrassment on people's faces when in a meeting and their IM app starts beeping like a time-bomb after someone has cut the wrong-wire.
The sender sending a short 1 liner and waiting for acknowledgement before proceeding would prevent this. (results in a single beep if the receiver is busy)
Its also avoided if the sender simply sends their entire query as a single message. (again results in a single beep if the receiver is busy and doesn't reply)
Also, there are people change the status to 'busy' when they are not actually available, extended lunches and what-not. And there are more people who forget to reset their status to 'available'. So setting status to 'busy' is no guarantee that you will not get a ping. Or a phone-call.