Or is it more like a Virtual Garage Sale?
If I have you over for a visit and you volunteer an opinion on my ugly couch, that's rude. But if I put that couch out in my garage sale and you stop by and comment in passing that it's the ugliest couch you've seen that day, is that just as rude?
Or, if I'm an artist and I put my work up in a gallery exhibit and you come to my opening, are you forbidden to say anything critical about my works?
I think a blog is more like a gallery exhibit than a virtual living room, at least for those of us who make stuff and show it to the world.
This all in response to the questions put forth on a famous blog and a less-famous blog recently.
My 2 cents. Unless you want to make your blog private and open your comments only to your nearest and dearest, you gotta be prepared to hear a few things you might not like. A private blog is more like having a party in your living room. A public one is not.
Now, if someone's being drunk and disorderly at the gallery opening, I might have security see them to the door. That's called moderating comments or banning someone. But I'd be hard pressed to ban someone for not liking my knitting.