I believe Darkcoin is the only coin that uses inverted block rewards based on the current difficulty (the exact formula is in the Darkcoin announcement thread).
What you meant to type is, Darkcoin is one of the few coins that uses a coin emission method designed from the ground up to be a pyramid scheme. The more hash you throw at it, the less coins come out, rewarding day 1 miners who got the 500 reward blocks even more.