I will give you personal first hand experience on these "ultra light" carbon fiber helmets.
DO NOT BUY THEM and expect them to PROTECT you. They won't. Remember all the buzz about the Nexx carbon fiber helmet? $600 and beautiful....
Yeah, protect you it will not. My buddy and I both have had several NEXX carbon helmets and a few weeks back we were at the boardwalk in seaside NJ when he had to do something with his hands so he put his Nexx carbon helmet between his calfs and a few seconds later it fell (a massive 9 or so inches) to the WOOD boardwalk. Entire helmet cracked up on that impact at .1 miles per hour. Just imagine at 65 hitting asphalt, concrete or a guard rail. I don't want to think about how the helmet wouldn't hold up. I would imagine it splitting apart like an 1199 due to its lack of conventional frame.
Now, I still ride everyday with my carbon Nexx everyday and will until I have the necessary funds to replace with a much safer helmet.
I can not speak about this exact helmet and am in no way trying to bash it- just sharing my experience with the Nexx carbon helmet. Oh yeah, do not buy a next carbon helmet. they fall apart with just regular use. No amount of weight savings is worth a concussion or death.
Just my $0.02.
Ultra-lightweight carbon fiber helmets are used in some of the most extreme racing applications out there, including MotoGP. For example, the AGV Pista, which weighs approximately 1200 grams and features an outer shell constructed completely of carbon fiber, is used by Valentino Rossi, Stefan Bradl, Pol Espargaro, Andrea Iannone, and Danilo Petrucci, among others. I have witnessed each of these riders be exposed to extremely brutal crashes at very high speeds without any reported helmet issue or head trauma whatsoever.
Like any product, there will be variances in quality control and features offered. In some cases, achieving an ultra-light weight may come at the expense of less protection, but this certainly isn't the case with all ultra-lightweight carbon fiber helmets. Helmet certifications such as DOT, Snell, and ECE help to provide a baseline from which to compare; but beyond that, additional safety and assessment programs, such as SHARP (as previously mentioned in this thread), will provide the consumer with additional performance information that can be extremely valuable when comparing protective performance of varying designs and brands.
The outer shell, or the section which is comprised of carbon fiber in said helmets, is only one component that contributes to the protective features a helmet provides. For the most part, the outer shell is primarily responsible for keeping the Expanded Polystyrene foam (EPS) intact in the advent of a tumble/slide, and for preventing penetration by sharp objects. With quality materials, this can be done just as effectively with carbon fiber as it can with the less expensive but heavier polycarbonate plastics, Kevlar, or fiberglass.
The EPS, however, is responsible for decreasing the deceleration of the head upon impact. In order for this to be done effectively, a specifically engineered "crush" must occur upon impact. The fact that your friend's helmet cracked upon impact doesn't necessarily imply poor protection; rather, it may in fact provide evidence that the helmet achieved what it is designed to accomplish - an engineered distortion. In this case, your friend's helmet displaying visible evidence of the damage could be a lifesaving occurrence, as some outer shell constructions are less likely to show exterior evidence of damage despite the EPS having been compromised. In this case, as with any case where a helmet is dropped onto a hard surface from any distance, it would be prudent for the helmet to be replaced or, at the very minimum, sent back to the factory for inspection.