Is there anything Zynga can do to reverse FarmVille's downturn?

While things may outwardly appear to be full of happiness and light in the world of Zynga's FarmVille – the game celebrates its (official) first birthday this month, and is, by far, the largest Facebook game on the site, sitting at around 62 million users – when you compare these figures to those found last March, which saw the game peaking at over 83 million players (32 million of which played everyday), that happiness and light turns bleak with sadness. But what is it, exactly, that has caused the game to lose over 21 million players in the span of around four months?