The problem with the songs she writes is that they never make it to either the final cut or the recording studio. Three months before "Circus" came out, I remember reading an article on Billboard about how she had been playing the piano and writing a lot of songs. I think "My Baby" was mentioned.
IKR? She writes enough every era for a complete album. I think that they never end up fitting with the album concept though. And in all reality songwriting is a bit overrated. I'd prefer to see her produce or something.