Protection of formulae : How often have you forgotten to protect the cell contains the formula that took you hours to test and perfect. It takes one instance of honest human error, and that formula is gone.
For pure data analysis, the spreadsheet is, indeed, king. To a point...Despite all of these extremely powerful features, the spreadsheet has limitations, which tend to manifest when you least expect it. Often, Murphy's Law applies and the spreadsheet falls over when you are right in the middle of a major undertaking, like month-end or meeting a tight deadline.
One user at a time : In the instance where there are a number of people required to work on a spreadsheet, they can only access it when no-one else is working on it.
You'll need to develop good marketing material. Things like demo videos, which you can find plenty examples on YouTube, screenshots, and keyword rich descriptive text help people find your spreadsheet and communicate the value that sets yours a level above the rest. Excelville.com actually allows you to upload your spreadsheet with all of this marketing material in an easily searchable and user friendly website.
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