Niches are all well and good, but some niches are never going to be big enough, or sell-able enough, to make anyone any money.
It looks like The Long Tail may have been a little out.
“Unfortunately, the tail’s not as long as one thought. One of Anderson’s most impressive statistics in his original article, that 57% of Amazon sales are in the long tail, was out by a factor of two. Oops.”