Where do breadcrumbs come from?

Not the crumbs left over on your breakfast plate, but the pre-packaged breadcrumbs that you can buy at the store. 

Are there bread factories that make fresh bread, leave the loaves out to dry, then make breadcrumbs out of those loaves?  Or is there a market for stale bread and a purchasing agent for the Better Breadcrumb Company goes around to the day-old bakery outlets and buys mass amounts of outdated hotdog & hamburger buns to be ground up into breadcrumbs?

These deep thoughts came to me while I was making my own breadcrumbs from some stale hotdog buns and dried out homemade bread.  You see, we still have quite a few eggplants left in the house and may even get about a half-dozen or more from the garden before a hard freeze finally does them in.  And since my first other-than-fried eggplant recipe went to the chickens, I figured I may as well stock up on the breadcrumbs so I can make more eggplant that Paul will actually eat:

Now THIS is how you're supposed to make Eggplant!

I will say that I have bought my own share of grocery-store breadcrumbs, but I think I'm going to start making them at home and keep a few gallon zippy bags filled in the freezer.  There aren't that many recipes I use that call for breadcrumbs, but it is a bummer to find out you need them and then don't have them around.  I once made some sort of recipe that called for breadcrumbs, realized that I didn't have any, then went to toasting sliced white bread & grating the toast.  I've also put Rice Krispies in the blender to make a breadcrumb-like topping.  Desparate measures, you know.  It did turn out good though.  I think.

I'd also like to make my own homemade stuffing / dressing for Thanksgiving this year, so I suppose I should also start messing around with recipes and finding out how many fresh loaves of bread I have to leave on the countertop to dry out to make the bread cubes.  Or I can just go buy them at the store.  But what fun would that be?