I dunno. With the plastic cover in place, the only "important" thing in the frunk that's exposed to your luggage, and vice versa, is the brake fluid reservoir. I'll agree that the frunk is a bit "icky" in principle because of its proximity to the windscreen washer fluid, brake fluid reservoir, air conditioning. Anything I put in there is usually in a backpack or plastic bag.
But, I can't think of any way to have items flying around in the frunk and damaging the brake system or aircon, short of having a spectacular rollover or crash - at which point you don't need the brakes or aircon anymore. On a similar note, I could also care less about my food shopping if the brake system inexplicably bursts and floods the frunk with brakefluid, leaving me without brakes at speed.
For me, this fits into the same category of non-concern as the fueltank's presence between the driver and passenger (even if it's below the chassis floorpan):
Nervous passenger: "What happens if we're in a car accident and the fueltank ruptures?"
Spots: "Well, for something to rupture the fueltank, it has to pass through us first. At that point, leaking fuel isn't going to be one of my major concerns."