Tee hee! This is about meeeee! I am the naughty drama-perpetuating Blooper, who evilly has my diary set up so people whose diaries I can't see also can't see mine. ;D Well, golly gosh, I actually have quite a few hardcore haterz who block me (or I did back in the day - only four left now!) and who would then stalk me, because they loved to read my drama. So I deprive them the pleasure of seeing it - or at least make it more difficult for them (they find ways round it, I'm sure!). Childish maybe - sure. But fun. This is Bloop, yo - no rules about being 'adult'! Bloop's the place where people can have fun being childish and creat dramaz, like, say, the Stay Classy diary and things like that! ;D Anyone gonna be continuing that diary, yo?
And yes, this also means FO people from whose friends list I'm excluded can't read either, but hey, how I see it is that if you (the generic you) don't consider me a friend and don't want to invite me into your life, you're unlikely to be wanting to read and be involved in the details of my life either. I stay MO so that any new people may get to know me if they want. I'm always open to new friends. But when you become FO you kinda close yourself off from new friends.
BTW, if someone has actually properly blocked you, rather than having their diary set up a certain way, it will specifically say 'This diarist has blocked you' when you click on their diary.