Here's my oversimplification on what it takes: Be relevant, be interesting, and be regular.
The last point in particular is important - if you scroll through the list of Biznik member blogs on this page, you'll notice right away that many of them aren't posting regularly. If you're going to blog, I think it's very important to post consistently, even if that's only a couple of times a week. That's where having a collaborative blog is nice, so that the pressure to post is distributed over several people.
Re: your last question, "If we subscribe to all of the Biznik members BLOGS does that add value to everything?" Well, first of all, that's a lot of blogs (currently there are 161 of them listed) but you COULD stay on top of that many if you wanted to by using a newsreader (especially since most of them aren't posting frequently). Nevertheless, unless you've got a lot of time on your hands, I'd select only the ones that interest you or that you find relevant to your field.
Here's how I show that I value a blog: 1) read it. 2) leave comments 3) link to it. And linking to it is what the blog's owner will likely appreciate the most, because it'll increase the blog's standing in Google and blog search engines like Technorati.