With respect to Mark's friends and family - It seems that this unfortunate event was caused by a compound of problems. First, I agree with you all that the sand did almost nothing to slow him down. Whether it was implemented properly is a good question. However, it appears that the net was the ultimate cause of the tragedy. He wasn't going very fast at all when he impacted it.
Take a look - Alexis Dejoria and Marty Nothstein's crashes, E-town 2009
YouTube - Marty Nothstien and Alexis Dejoria Englishtown Crashes 2009
BOTH of those cars entered the sand traps and a higher rate of speed than Mark did, and in Alexis' case, it was MUCH higher. Do you notice though, that it appears that the nets were way less "tight" than the one Mark came into contact with? Marty went through the first net and was stopped by the second, Alexis blew right through all the nets and was stopped by the sand barrels.
Granted, it is an apples-to-oranges comparison, as they had Funny Cars and his was a dragster. But it still looks like, to my untrained eye, that there was a vast difference between those two sand traps and catch nets.
Such a sad event that could have possibly been avoided if there was a standard on sand traps and catch nets.