On a Thursday, a couple weeks ago, I wanted to ask a friend if he wanted to meet with me on Friday morning. It was about a quarter past midnight and I was on the horns of a dillema. How should I contact him?
Great post. I think you should explore this further.
In any case, today emails are totally asynchronous. Since other messaging is so instantaneous, email is culturally treated as "reply when you have time".
My etiquette is that Facebook messaging is always fine. It is different to regular sms in means that if a person wishes to be always in contact to the 'outside', non-friend world (work, etc.) it will be very legitimate to have sms sounds on, even at night. It is a much more 'required' means of communication, than facebook messaging. When you have facebook messaging sounds on at night, that's you saying "please interrupt me even with the dumbest, most non-critical reasons". It is something most people definitely have a control over.
I also don't have a mobile phone, for pretty much the same reason. My wife has one, but it's strictly sound-off, so she decides when to look at it. I also don't have a Facebook account. I do have a landline phone, but it remembers calls and lets me return them as I want. So, I can surely relate to what you're saying, but at the same time, I don't have much to say, except that it's perfectly possible to live asynchronously. :-)