1. Often times the product is a leaky bucket, and you experience a massive spike in traffic and very quickly see your growth asymptotically approach zero.
2. These platforms often times also are filled with people waiting to abuse your platform. For flurly, all of my original fraud problems originated from my product hunt launch.
Thus for GraphJSON, I went with a different approach. I shared my progress on my twitter account and mostly had my builder friends use the product. Over the past 6 months, the product has continually improved due to the constant feedback of this community. Word naturally spreads and so does the growth.