what does privacy really mean?

i'm beginning to find private blogs particularly appealing lately, not that i've been invited to anyone else's but wooimin's, but the mere idea of it somehow makes the blog a little bit more interesting to people who are actually out of the loop. not only does it impart a sense of exclusiveness but also the issue of boundary as in where to draw the line between sharing your thoughts with the world and your circle of friends.

and so i ponder, what are the possible reasons for one to privatise his or her blog? is it true that
as one's thoughts get more personal and intimate, the mind also gets more insecure subsequently? hence justifying the need to cut other people from your life? or does the writer has a secret so deep that it becomes a burden to keep it in her heart and blogging becomes a possible channel of release? like a closet of secrets. i find the irony of a privatised blog seemingly amusing, its like another way of saying, 'hey i have a secret, but i'm not telling you what it is'

which brings me to another point of whether secrecy is overrated in our society. how many times have we heard of, ' hey, i'm actually not supposed to tell you this, so just pretend you don't know anything' ? the threshold of secrecy is without a doubt, questionable, nowadays.
just look at postsecrets.com and the underlying reason for their popularity and success. that should have given anyone a hint.