When does a blog stop being personal and start being real (corporate)? When you take on numerous guest bloggers? When you and the guest bloggers use the site in large part for promotion of your professional endeavors? When your readership rivals that of some magazines and journals of opinion? When you hire employees to help you run your blog? When it constitutes your primary source of income? When you set up an LLC to handle the legal aspects of your blog?
As someone who has conducted very personal relationships publicly on a blog, I have been tempted to delete references to previous associates wholesale, if only so I could peruse my own archives without a twinge of pain and embarrassment, but I haven't, because I own my past. Any changes in my opinions of particular individuals bear on who I am going forward, not who I was.