In reply to Flinticus:
Just to follow up on my hasty reply last night, I have found corkscrew design pegs have good holding power in soft, sandy terrain, and they are tough when they need hammering in to rocky soil.
In particular, the Lightwave ones are strong, and MSR Cyclones are strong and have a useful leash. I have some Sea to Summit Ground Control pegs but their heads are very soft - unlike the MSRs and Lightwaves, they do not have any reinforcement - and don't take much hammering with rocks before they deform. Hilleberg Y pegs are strong and seem to hold surprisingly well for their size and design in soft soil.
A Hilleberg tip I have not tried is to use two pegs in line per pegging point, one 10cm away from the other, attached to it by some guy line, so that the loading is distributed to both pegs.