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.
All of these things pull you away from the thing you really want to do...which is to build and sell great spreadsheets. The best thing to do is use Excelville.com since they have web developers and internet marketing specialists to help get exposure for your spreadsheet.
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.