I know this has nothing to do with development but I always wonder if there is an etiquette for responding to emails. I understand if people are busy and they can't respond right away but how long can I wait before I have to respond? Or from the other side of the coin how long should I expect to wait before people respond back to me? To me this is one of those things that I think even if you are busy you should at the minimum acknowledge the email. I feel at least doing that you let the person on the other end know "hey, I received your email and I am thinking about it" or whatever. You get the idea. Just something to let the other people know you haven't forgotten about them or overlooked them.

What do you think? What is appropriate? Is this just me being a little obsessive?