[cagey]

Maybe your co-workers and clientele are all skilled typists who never make transposition errors. But I've dialed enough wrong numbers due to simple transposition (mental) errors (and made analogous typing errors) to know how easy it is to make them. If 'persons unknown' had to move my personal investment account number around via data-entry, I'd feel much better knowing they were copy-pasting and not manually transcribing.