Increase Search Traffic with Horizontal Content

Those new to blogging or article writing have often been told to focus on one very niche topic. One narrow vertical. That has commonly been considered the way to gain credibility, readers, links, and ultimately traffic, which assuming the blog/site itself isn't your primary source of income, could lead to sales of your products/services. But is keeping it narrow really the best way to go? For some, it is. Another way to go would be to cover as much ground as you possibly can. Throw a wide net out there and see what you catch. Once you see what you've caught, maybe you can catch more in the same area. The thinking is that the more ground you cover, the more people you are potentially exposing your work to. It's going horizontal, rather than vertical. Do you think you could find greater success by keeping it narrow or broad?