Seth Gottlieb, of Content Here, posts some very good points about the extent to which you should separate the management of your content from the systems that actually publish them for your online audiences.
However, as I have warned in earlier posts, the flexibility may not be worth the cost for all publishers. Unless your business model depends on aggressively leveraging your content and you can afford to play on the cutting edge, a lighter weight “website in a box” style architecture may give you the flexibility you need without the additional complexity and cost of building and integrating these de-coupled systems.
In short, you have to balance elegant engineering with the value of the outcomes you are pursuing with your web site. If you are in the content publishing business and are of sufficient size, then extreme separation can pay off in a significant way. Outside of those two conditions, a pursuit of architectural elegance may actually be counter productive for your needs without sufficient return on the big investment it requires.