The great horizontal killer applications are actually just fancy data structures.
Spreadsheets are not just tools for doing “what-if” analysis. They provide a specific data structure: a table. Most Excel users never enter a formula. They use Excel when they need a table. The gridlines are the most important feature of Excel, not recalc.
Word processors are not just tools for writing books, reports, and letters. They provide a specific data structure: lines of text which automatically wrap and split into pages.
PowerPoint is not just a tool for making boring meetings. It provides a specific data structure: an array of full-screen images.
Via Spin the Cat [1], “How Trello is different - Joel on Software [2]”
In the past, I've given Smirk grief over his use of Excel [3] to make what I called “glorified text files,” but I see he's not alone in using Excel for tracking lists. In fact, I suspect that if the entire calculating engine of Excel were excised, not many people outside the financial realm would even notice (and the financial system would probably be better off too).
So it looks like Joel [4] has a point—spread sheets provide a type of data structure, and people use it as such. Looks like I'll have to cut Smirk some slack now. Sigh.
[1] http://spinthecat.blogspot.com/2012/01/horizontal-killer-
[2] http://www.joelonsoftware.com/items/2012/01/06.html