If a referenced cell is deleted using Delete row/column/sheet command
the former dependent cells show #REF! without a hint where it pointed earlier.
if these cells are on another sheet this often fatal result of an editing operation remains undetected for a long time.
reconstruction often takes hours if possible at all in big sheets.


simple example to reproduce
A1=1
A2=2
A3=3
A4=A1+A2+A3

now delete row 2

A4= #REF!
and shows =A1+A#REF!+A2

suggestion: 
In case a #REF! is detected a popup message should be raised
"Do you want to delete  referenced cell(s) A2 ....?"
YES/NO - where NO is default.

Hope this makes sense for an "office" product.