the narrower your content focus, the more likely you are to drive sharing and subscription behaviors, because itís more likely the reader feels like you are talking directly about their situation. And the content is more relevant more often. The trade-off is traffic.
Broad Topics = more visitors, less sharing, less subscriptions
Narrow Topics = fewer visitors, more sharing, more subscriptions
My first observation is that while a broad topic site may get more traffic overall if you segment that traffic by site category those numbers might well look closer to the narrow topic site. Without the sharing, without the subscriptions.
My second observation is that subscriptions are not limited to blogs or other CMSes. Given his mention of 'blog' in his title thought I should make a point of emphasising that RSS, newsletters, et al are optional services for any site.
And my third observation is that there is no requirement that subscriptions be whole site.
And that means that (as always, when done properly) one can have one's cake and eat it too; one can have a broad(er) topic site with more overall traffic opportunities AND more subscriptions for traffic retention.
This is not a new concept, enterprise sites, especially news sites have been doing this for years.
Note: IBM has zillions!!!
Of course it takes more work. More content. In the same amount of time. So, it becomes a business decision: is the ROI sufficient? Will the effort develop the necessary minimum additional subscription conversions to cover the costs involved? What other considerations are in play? Etc.
Note: existing sites with deep archives can run repeats just like TV.
Nothing earth shattering, no great secret to internet success, simply one more arrow in the quiver of possible solutions.
p.s. there are always exceptions.