Why people share intimate details in their blogs
I think personal blogging feeds off the same mentality that make people call help- and hotlines, go to support groups and seek company in chat rooms. The craving for listeners whos feedback we can be selective about accepting.
It's a lot easier to block out negative feedback from a total stranger than it is from your family and friends. If you share a character flaw, depressions or dark secret with someone you're likely/forced to see again the stakes are high. What if they'll think less you? Or get mad at you? Or get hurt?
When sharing with strangers you don't have that fear. If you piss them off, so what? There's likely to be no consequences. And chances are that if they do get pissed off or think less of you that you won't ever find out.
It's an excuse, arguably a good one, to get stuff of your chest with a sense that someone out there is listening. Caring. Understanding. Who wouldn't want all those nice things at zero, or nearly zero, risk?