Why can't I sync more photos to my ipod touch? I am trying to sync all of my photos to my ipod touch. it syncs some of them but now when I add more folders it simply fails upfront saying:

No photos were copied to the Ipod because there is not enough free space on the ipod to hold your photos and photo albums.

I have 12 GB free so I understand if all can't be synced but why doesn't it sync as many as it can until the ipod is filled up ??

Is there any way I can figure out how many photos it will let me sync to avoid wasting time trying and failing ??
As you have figured out, you need to select fewer folders/photos in order to keep it from failing. Simply compare the size of the folder(s) you want to sync with the space available on your iPod.

On a Mac, you can select a folder and press command+i (or control+click and select Get Info) to display the size of a folder.

On Windows, you can right click and select Properties to display the size of the folder.