There's a new Gamasutra article written by Russell Carroll (Reflexive, GameTunnel) about increased profitability for developers and small studios from not innovating - making lots of money by creating clones of existing games which are popular.

According to him, a Hidden Object game, Click Management clone (Nanny Mania), and a Match-3 game sold nineteen copies more than a title belonging to any other genre, based on Reflexive Entertainment's sales statistics from the last three years. Essentially this means that developers who put out a clone tend to sell at a ratio of twenty copies as opposed to just one if it was based on anything resembling an original idea.

- Cloning Created the Casual Game Business