It doesn't have to be all or nothing, does it? People can have a bit of a break when life offline gets busier, or if they are just tired of posting for whatever reason. It's not as if they are moving to the other end of the country (and even if they do there is likely to be internet access?).
If someone decides to leave (as opposed to just not posting for a while) it is usually after something unpleasant has happened, and on the whole the memory of these things fades with time, so the poster decides to come back. It's more difficult to do this if they have 'flounced', though, so on the whole people quietly go off and lick their wounds, then either come back, find a different board that suits them better, or retire from internet discussions in favour of another way of filling their time.
I can understand asking after a poster who's vanished, particularly if she has been prolific, as in any community the dynamics can be shifted if the 'personnel' changes, and also as we feel we know people with whom we interact on here; but I wonder if too much of a 'post mortem' makes it less likely that someone will come back, particularly if people have made negative comments about someone who may already be hurting?
) and knowledge. Certainly on some subjects it was detailed knowledge.
