I think the definition you linked to is a bit too broad in its definition; by that definition, cnn.com is a blog. (Granted, it's commercial, but that didn't stop you from calling /. a blog, did it?)
I don't understand this strange trend to classify all online publishing (colloborative or otherwise) as a "blog." I think when people typically think of a blog, they think of a online journal of sorts. It's a subtle difference, but I think it's important. Otherwise, everything is a blog. And that's just silly.
Incidentally, it reminds me of the whole hubbub in the corporate world over enterprise portals during the last few years. No one can quite decide what one really is, but I'll be damned if I don't want one for my company!