My parts are generally sorted (box of pedals, box of seatposts and saddles, bin of freewheels and cassettes, fishing tackle boxes full of small parts, etc.) but not inventoried.
I did take a partial inventory this past fall in preparation for selling some things at Veloswap and that was handy for keeping track of sales, but I don't see much reason to keep a running inventory of everything since most of the time I only sell complete bikes.