[jbergens]

This doesn't scale well. If only one person edits the spreadsheet and that person knows how to save copies and make sure there is only one latest version it may work. If you give this to 10 people they will start making copies, saving those with different names ans save the copies on some server or on their own machines and after a while you don't have a single source of truth anymore. And you almost never have logging when many people edit copies of Excel documents.

[allenz]

That's true. Currently I handle scaling by automating nearly all the work. Most routine transactions are automatically categorized without manual input; I just skim the report. We modify 0-2 transactions/day, which is low enough for Dropbox to work well. This wouldn't work for a Fortune 500.