Well said. In addition to that, I use my blog to host content I hope people will find via google, like how-tos or coding gotchas. I'm not going to post a coding trick to my facebook account, even if it has more active readers.
Exactly. Some content, like status updates, is perfect for Twitter or Facebook, but this article seems to assume that that's all anyone uses blogs for.
Please god say it ain't so. I would like to think that people who keep blogs (at least the subset thereof that also read Wired) tend to write more interesting things in them, and I can't imagine that being replaced by 140 characters (this notwithstanding: http://twitter.com/_why/statuses/881768089 )