Long ago working for a retail store chain, I made some excel DSL to encode business rules to update inventory spreadsheets. While coding I realized that their excel template had a bunch of cells with whitespace in them on row 100000. This forced excel to store the sparse matrix for 0:100000 region, adding 100s of Kb for no reason. Multiplied by 1000s of these files over their internal network. Out of curiosity I added empty cell cleaning in my DSL and I think I managed to fit the entire company excel file set on a small sd card (circa 2010).