I think the biggest concern is the day you try to expand beyond the niche. When you do that, you realize that your product has been so focused on one niche that

I think the biggest concern is the day you try to expand beyond the niche. When you do that, you realize that your product has been so focused on one niche that it takes a major effort to grow your product. So, anytime I build a feature I ask myself if this is something that we could scale to another group of people outside of our niche. Regardless, I think going after a niche is a great strategy. Crossing the Chasm talks about the value of niches a lot. My major concern would be building in a way that limits your future growth options.