The labels of empty fields should be hidden, but in this instance Feeds seems to keep them there.
This bug was referenced and patches were submitted for the 7.x-2.x-alpha3. (http://drupal.org/node/1107522)
This is a patch for field.inc in feeds/mappers
It solved my problem and now hides empty fields on import.
Do not create duplicate issues for different releases. All should be worked on in the same issue. It's best to start with the newest patch, and then upload backported patches once the one for the latest development branch has been completed (if there is still interest). Please re-post your patch over there.
Drupal is a registered trademark of Dries Buytaert.