I think that part of the reason I don't email fb is that so many times when I have, I received no response. At least on lj, you can see your comment. There it is. You know the person has received it, even if they choose not to respond to it (which I personally find tacky, unless you've got a bajillion people reading your journal and just don't have time to respond to all the comments, which I do understand), but when I don't receive a response to an email, I think--Did they even get it?