Created attachment 69713 [details] The panel Icons don't scale to panel size, if the panel is sized smaller. This bug aspired since KDE 4.8.1. This worked with the older version.
This could be caused by one of the widgets forcing a minimum panel size. Try removing one of the widgets from the panel to see if this is the case.
Finally I could find the not scaling widgets. It is the Folder View widnget.
*** This bug has been marked as a duplicate of bug 295531 ***