I don't care if it's a bag that is the most durable, structured kind in the world. The reasons why I wouldn't let anyone borrow my bag, no matter what bag it is or who it is, are:
1.) Even w/ the durability being top notch, there would still be room for another small scratch or so here or there when I get it back.
2.) Bags are extremely personal to me, and I'd like all the usage to be mine, not anyone else's - at least from the date of my ownership. This is just like how I'd like all the wear and tear to be mine, not anyone else's.
As a matter of fact, I may consider buying a brand new version of the most expensive bags (which is going to be double the price) that are on my wish list instead of ebaying for them as I thought of doing before.