I just noticed that a lot of the podcasts that I have listed in iTunes had not been downloading new shows. Also each of these had a exclamation point icon next to them. At first, I though that this was because the rss feeds were not being parsed by iTunes. When I clicked on the icon, I saw this message
It looks like iTunes stops downloading podcasts if you don't listen to the shows. I assume that Apple did this to prevent podcasts from filling up the disk. This is fine, except it stops downloading them even if you manually delete the old files. I think that they should change this to only stop downloading the new podcasts shows have not been listened to or have not been deleted.
In addition to that, iTunes should notify you that it stopped downloading podcasts.