Can a Weblog Be a Forum?

That's the question. And it arises since Clarin.com from Argentina has set up a public weblog, where anybody can add a comment. The weblog site is hidden in a tiny link on the front page, which takes you to the weblog front page. There you can see news items, all of them about technology issues, and you can post what you think. As in a forum. So, can we talk about this as a weblog? What's the difference?