This is getting to be an important question and one, it seems, that I might even have some experience from which to concoct an answer. As is public knowledge, one of the companies I co-founded, BackBeat Media, represents Think Secret's advertising. As such, we're very much aware of all the news coverage surrounding Think Secret, and a lot of that coverage has referred to Think Secret as a blog. The fact is, Think Secret has been around longer than the word "blog" has been used in this context (of course, it was first used by Dr. Seuss in 1953). Anyway, all of this has caused me to spend some time thinking (and ranting!) about the definition of a "blog". And, to me, Think Secret couldn't be further from that definition. A blog is a web-diary, written by one person, sharing his or her direct views, and basically having an asynchronous conversation with his or her readers (usually by way of comments or trackbacks). Some examples of true blogs would be those written by Robert Scoble, Doc Searls, David Parmet, Darla Sasaki, Jason Calacanis, and Dave Winer. You'll notice I don't even mention the *name* of the blogs, because really a blog is about the person who writes it. Surely the blog itself can have a specific guiding message or purpose, but it's about a personal point of view. While I can imagine it being possible that a blog could have multiple authors and still be a blog, it would have to be such that each writer had their own distinct personality, separate from every other writer. Possible, but not altogether likely or common.
Some sites that shouldn't be categorized as "blogs" are Think Secret, The Mac Observer, Engadget, Autoblog, (and really most Weblogs, Inc. properties), and Gizmodo. Sure, a lot of them use software/rendering/publishing engines that are either used by blogs and/or appear the same, but the content has nothing to do with that of a blog. It's news, plain and simple, presented by multiple people (most of whom are employed to write it), and often times in written in the "anonymous group" style ("we found this", "our experience is..", etc) where there is an overall personality to the site, but not a distinct personality attached to each author.
It's a pretty clear distinction, and hopefully the rest of the world will figure it out before it's too late.