Some people are finding that the Notes section of the attribute editor in the newly released Maya 2012 may always stay “open” or unfolded even when you squash the notes field to conserve viewing space in the editor. I do remember this happening in a previous version of Maya that seemed to be fixed pretty quick, however I am uncertain which version it was.
Having said all that, David Johnson from DJX has noted of a simple MEL command from ginodauri on CGtalk that will hide the Notes section. The command is simply: layout -e -vis 0 AEaddOrEditNotesLayout;.
However David has taken this a step further and added a menu item to the List menu in the attribute editor. This script that places a drop down menu in the attribute editor to hide the notes section can be found on his downloads page here.