1) We're open to outside world. You don't have to be a Resident to read 'em....
Right. You are aware that the majority of (or at least tons and tons of) forums out there allow public read access?
2) Simplicity. The information presented is in a cleaner format, making it easier to get to and cutting down on the confusion.
This is ENTIRELY your personal opinion. Some of us get so frustrated with the linear format of, "Blogs," that we don't bother to read them at all despite what great content we might be missing. I believe the person you were responding to is one of them, which means I am not alone in this. Opinion. How would reorganizing the forums not solve the same problem?
3) Distribution. After hearing complaints about the limited usefulness of our forum RSS feeds, the blogs provide a superior way to subscribe to live news so *you* can hear what's going on.
I'll admit I am not completely sure on this one. I do however know that that thread subscriptions have worked pretty darn well in the past for me. Also, the SL forums to a crappy job of marking threads read/unread. I suppose this might be because you don't want to store per-user data server-side? Other forums I have used actually keep track of what threads/posts each user has read (though they allow you to automatically mark read posts older than a certain configurable limit). Beyond a single session that is. Of course a, "Blog," won't even do as well as the SL forums do now on this front unless you want your e-mail address SPAMed.
4) Ability to directly reply to announcements. Can't do that here! (This is going to be more important in the future.)
Can't do that presently, sure. How exactly does the blog offer more than allowing replies on announcement threads would?
5) Loads quickly. The forum loading can be pretty bloated compared to the streamlined blog content. This is especially important in those "OMG! WHAT'S GOING ON???" times. As we know from what happened yesterday.
Stream...lined...you mean getting absoultely all source content at once instead of neat link titles? Err....
6) Linden posts don't get lost. Hundreds (literally) of times, I've seen Linden writing be buried in the forums. Even some super-informative ones. So news gets missed, we hear many times about "Where did you say that?" and it's been a longtime, soretooth problem. All I know is from my experience. The blog makes it much more obvious and easy to be informed--and we can never do that well enough, so I'm content we have it up.
Sounds to me like people aren't making adequate use of stickies. What?
7) More effective to respond to Residents. There's a misconception blogs are one-way--not so! When you lay yourself bare on the Internet, you invite dialog and discussion. Many of our existing blog posts are directly in response to Resi concerns in the community, and more to come. And again, that loops back to #6. I was a skeptic at first, but I'm becoming more of a believer through actually doing it. (Part of this is because of my own personal blog, which has greatly facilitated my understanding.)
This isn't a reason to use a, "Blog." It is a counterargument against NOT using a, "Blog," so I'll leave it alone.

Maybe for purely informative non-critical news updates, sure. I haven't run into a company that depends on them for directly responding to important customer feedback, but maybe you have more experience there than I....
Anyone reading this who's not visited yet, I warmly welcome you to....
I think perhaps I have when people have annoyingly posted only links there instead of real content on the forums, yeah. Otherwise....