I wanted to have more free space on my MacBook Air’s internal hard drive, so I moved drives iTunes media folders (i.e. Books, Mobile Applications, Movies, Podcasts and TV Shows) to my external hard drive. Then I used symlinks to link the old locations to the new ones.
Accessing my media is not a problem in any way, but when it comes to updates or new podcast episodes this will simply not work out.
Application updates and podcasts will be kept in the downloads folder within the iTunes Media directory on the internal hard drive. They won’t get moved to the right location and so iTunes still shows the apps as outdated (i.e. I could start the update again and the files will be stored in downloads once again)…