While Co-Authoring for products like Word and PowerPoint may be desirable, it is a horrible idea for Excel. Spreadsheets are complex objects with numerous linkages that may or may not be understood. Allowing one user to change a cell without understanding the impact it may have on a formula elsewhere, even on another sheet, is a recipe for disaster. A problem might not be discovered for a significant period of time meaning that versioning is not a sufficient backup. In addition, the related Autosave necessary is also inappropriate for spreadsheets. It is common to open a spreadsheet and want to analyze what would happen if something different was done or something different was entered. Autosave will destroy to production spreadsheet which is not the intended effect.

Excel should not be set up to utilize Co-Authoring. This is preventing us from utilizing OneDrive to move our serve to the cloud.