I read about Office 2000's dynamically hidden menu items feature (with the expand button added to the bottom of each sub-menu) somewhere, that the items that _a

I read about Office 2000's dynamically hidden menu items feature (with the expand button added to the bottom of each sub-menu) somewhere, that the items that _are_ shown initially were determined by collected usage data. So it's probably aggregation that makes the most sense, not digging into each individual user's behavior.