I'm right on with Adrian Holovaty on why news sites don't need specialized blog systems:
I highly recommend integrating a self-built [weblog] system into your legacy CMS, if you've got the means to do it. Ideally, if you've got a good CMS already and it's customizable enough, just extend it to produce "blog" output. Honestly, weblogs are nothing special -- they're just another form of article.
Taking this one step further, this isn't just true for news sites, it is true for any kind of site that already has a CMS which can be extended to support weblogs.
Weblog systems are a simple form of CMS, specialized to handle weblogs. I believe that soon, the quintessential elements of weblogging (like those plus comments, RSS, TrackBacks, etc.) will find a natural way into many CMS systems, whether they are commercial, open source or custom. Similarly, weblog systems will be pushed to their limits by people who want to do more than a weblog. One example of this trend is Boxes And Arrows. This is a web site, not a weblog. Only when you explore the clean layout does the underlying weblog system appears, in the form of comments that are nicely promoted as conversations and, of course, the credits to MovableType in the footer.
Eventually, the technical frontiers between weblog systems and CMS will vanish, leaving perhaps to niche players some marketing delimitation to distinguish between the public users (the current blogger crowd) and the corporate users (the current CMS market). Ultimately it is about creating and publishing content, which is what content management systems are made for.