Agree, but willingness to answer also has context. I'm almost always willing to answer simple questions such as "Where can I find XYZ?" I have to be in proper mental state to answer more complex questions such as "Can we discuss the large and complex proposal I sent via email yesterday?"

This is all amplified when you have virtual teams. Those more complex conversations are more manageable when you are face to face. People can express how busy they are and how focused they are. IM doesn't have that luxury.

"Can I ask you a question?", in my personal experience, is usually a trap. If it was an easy question, the other person would have just asked it. Therefore, it's probably going to be a complex question that will take time and focus.

True, but 99% of the time I'd prefer someone just ask me the question and provide the context they think I'll need to answer it. This makes it much easier to come back to my desk after being away for hours and be able to help you out immediately, rather than wait for you to be available, then wait for you to type the question, etc.

If more context is needed then it will have to be asked for - but this is no different than the first situation ("Can I ask you a question?"). Simply asking the question will optimize the response and conversation time in most scenarios, and will not slow it down in any.