App Economy

I must admit that I have spent a lot of time on my online farm growing grapes and coffee. I have also grown many a vegetables and even grown flowers. The best part is I have made a boat load money doing this, more than I have made in real life. In case you are not following me, I am talking about FarmVille, a Facebook game by Zynga. Recently I find my interest in this game fading and this has gotten me thinking. What could Zynga do to keep me engaged and also monetize FarmVille while doing the same?