I think thats the right title.
What, why, how?
I post on STW sometimes, I have my own website that blathers on about trips I have done or am about to do, I have a facebook presence that basically unused. Why?
What do people get out of it? Why do people blog etc, does the greater population care what cd or book a stranger bought or read. Do people have an alter ego (I know lots do on here 
) that they wish to be perceived as and why does it matter as you will never meet most of the people who notice your post.
Its a discussion we are having here in the office and although I am part of it I'm not sure why, in my case a bit of a hobby, a way to keep people who are coming on trips informed.
And as a case in point why am I posting this on an online forum to people who's opinions may help me get an answer to this but I will probably never meet most of you.
& no the answer is not that I am trolling or looking for an ego boost
