Interventor,
I'd like to expand a bit on your definition without stepping on your toes, if I may.
A "Blog" is usually meant to refer to a venue where one person (the blog's author) makes entries and others (the blog's readers) make comments on those entries. A blog can have a theme, such as the NY Hack blog which is run by a female cabbie in NYC. That blog chronicles her days and nights of being a woman driving a cab in the Big Apple. There are also Pop Culture Blogs like
www.Idontlikeyouinthatway.com and
www.perezhilton.com that keep up with celebrity scandals.
The blog mentioned in this tread
www.blogs.abcnews.com is a sort of dumping ground for ABC's news items and provides a place for people to comment on them.
The Times Daily Forums is, as the name suggests, a fourm. Forums are for holding discussions and posting user generated content. This would differ from a blog in the sense that there isn't one common thread and there are several authors commenting on vastly different topics.
Hope that cleared things up for anyone who was still in doubt.