We have a known issue where not all of your plays from the Zune HD device upload to The Social. Unfortunately, there is no workaround at this time. We plan to fix this in a future version of the firmware, but haven't announced a timeline for doing so.
Note that this issue doesn't affect previous versions of the Zune players, and we don't know of any systemic issues with play uploads from other devices.
Jessica Zahn, Zune Social Program Manager ~ This posting is provided as-is with no warranties, and confers no rights.