He didn't use the same terms, however, and he didn't apply the insight to products and sales.
Do Web Sites Have Increasing Returns?
Zipf Curves And Web Site Popularity
Diversity Is Power For Specialized Sites
His blog usability guidelines are good, too, but I totally disagree with this one:
8. Mixing Topics
If you publish on many different topics, you're less likely to attract a loyal audience of high-value users. Busy people might visit a blog to read an entry about a topic that interests them. They're unlikely to return, however, if their target topic appears only sporadically among a massive range of postings on other topics. The only people who read everything are those with too much time on their hands (a low-value demographic).
The more focused your content, the more focused your readers. That, again, makes you more influential within your niche. Specialized sites rule the Web, so aim tightly. This is especially important if you're in the business-to-business (B2B) sector.
If you have the urge to speak out on, say, both American foreign policy and the business strategy of Internet telephony, establish two blogs. You can always interlink them when appropriate.
I think it's probably true, but I think his priorities are wrong. Building a loyal audience is a fantastic thing for networking. With a blog that's only about a business topic, winning a subscriber is just "hey here's my card buddy here's why I'm worth talking to." With a blog that's about a gazillion different things, anybody who reads every single post by definition is going to have more shared interests. I'm not saying reading my blog makes you my friend in real life - it doesn't - but it goes a lot further down that road than a blog which is all business, all the time. It certainly makes conversation at conferences easier. It's also much more valuable for employers and/or clients who want to research me before contacting me about business. In fact, a conservative Christian political organization interested in my Rails skills contacted me last year, and I was actually insulted that they bothered to waste my time, when my political views are so easy to ascertain.
More importantly, though, although I believe Nielsen's analysis is correct, his assumption that a loyal audience is a priority is absolutely dead wrong. If you're a restaurant, do you need every customer to visit every day, for every meal?
Besides, even if I agreed with the guideline, it would be literally impossible to implement. My blog veers across such a wide variety of topics that implementing every topic as a separate site would require tens or even hundreds of sites. That's what tagging is for.
The assumption that topic filtering happens at the author's end, not the user's end, is the assumption that killed Yahoo and made Google king. Clay Shirky explained this years ago.