http://use.perl.org/ has user journals which are certainly blogs, IMO. It also has non-journals which form a forum and are not blogs. I'm baffled by the previous claims that slashdot is a blog. Note that the previous poll said "blog / web journal" to help clarify what was meant by "blog".
Nearly every "blog" I've seen was a series of items written by the same one person with no one theme overpowering the "theme" of authorship. Not that I claim to have seen a large percentage of the blogs in existance, but I've seen no small number of blogs and the vast majority were "personal". The proliferation of tools to help people publish their own blog has lead to people using such tools for non-journals or at least not-personal journals. But I consider such to be "using blogging tools" for non-blogging (such as publishing a bnewsletter).
So I don't broaden the term "blog" to cover all manner of web sites with dated articles, because that'd make "blog" a relatively useless term. I stick by (near as I can tell) the original meaning where I think the single-author aspect was an important part of the definition. I'm quite sure the rest of the world won't keep "blog" narrowly defined (and thus useful), however. :)