I don't want to read details about someone's marriage problems, or constant exhibitions of their depression or anger issues.
Have a bad day and by all means, blog your heart out, but have it be part of working through the issue, not just word vomit every day about how much you hate your life. If a person is in a dark pit of anger or despair every single day they need to get help and not just vent constantly. Again- venting is fine, but remember to count your blessings every so often.
I think people need to realize that anything you put online can be seen by anyone and if you wouldn't talk about it with all of your neighbors, it's probably a good idea to mark those posts as private. I am always amazed at those who are super offended when their blog posts come back to haunt them and how violated they feel when they throw something horrible out there with no thought to the fact that the internet is public.