Then again, I can recall some entries on here where I was deliberately vague so as not to make certain content accessible to readers... so then what's the point? If I can't read back through this and get a comprehensive, brutally honest account of my own life, then this isn't really fulfilling the role of a diary. Is blogging just posturing? Are we (consciously or subconsciously) picking and choosing what we write about in order to appear interesting to potential readers? I don't think that's exactly the case either; a lot of what I (and other bloggers) write about is mundane stuff, and generally I don't see a lot of hesitation to vent about less happy times.
I think humans have an innate feeling of self-importance that drives them to record and savor and revisit past times. That sounds like a criticism, but I don't mean it that way entirely; I think we're painfully aware of our transient nature, and so we strive to record ourselves in the world because it makes us feel like we exist more. Some people take pictures of themselves everywhere they go, some people keep a voice recorder in their pocket, some people write and reflect on their experiences and emotions, because all of these things serve as proof of life. They say "I am here, and I matter."