[kenpachi]

You really have to pick a niche that you are passionate about, otherwise you'll lose interest in it too quickly and stop short of generating some revenure for something you like to talk about.

I don't really buy into the argument "you need to know you niche", you're probably just as well off not knowing, because you'll have so much more to write about when you start learning it.

As long as you choose something that you don't find boring or hate, anything is fair game.