Many of our users do not immediately realize that a section has been collapsed (especially if they unknowingly click on the section to collapse it). They then think that the section simply contains no data/fields. Visually there are no good indicators telling the end user that the section has been collapsed.
Yes, there are the up and down carets but those are easily ignored or misinterpreted (not to mention that they are backwards in their execution--if a section is collapsed, shouldn't the caret be pointing up indicating that the section has been collapsed up into the section header?).
It would be good to either use completely different icons to indicate the collapse/expand state and even use a different color scheme to further make them appear different?
I've helped many users through this issue because it is unclear when a section was collapsed.