Good points. I would imagine so long as they can engineer a sealed compartment it won't be that bad in regards to snow and sweat. On some of the interior shots it looks like one's head rests directly against the cardboard lattice/grid structure. Cyclists certainly sweat so I wonder what's going on there. Assumably, still an R&D issue? Preventing UV damage can't be insurmountable, I would think.
The thing I like about the idea is that with EPS it's really hard to tell if you're compromised because of the outer shell, mesh, pads, etc. I feel like it would be pretty clear when a cardboard helmet is compromised. I think of that as a solid advantage.
The single impact design is a little worrisome, I agree. But with potentially a much cheaper production process I imagine it being quite cheap to get a replacement.
But, all told--all agreed. Sweet concept with great potential.
FYI: original article I saw is here: http://www.core77.com/blog/materials/ani_surabhis_biomimetic_kranium_corrugated_bicycle_helmet_is_stronger_lighter_than_traditional_eps_23981.asp