The speculation about wake turbulence contributing to the stick shaker is interesting but I would have to ask whether an A380 could do this to a 747? An A380 throwing around a Challenger is understandable given the relative sizes, but if it is possible for an A380 to get a 747 close to the stall then there has to be a serious rethink of wake turbulence separation in a holding pattern! LS states that he experienced mild encounters which I assume was from other 747s. If it was an initial encounter with wake turbulence I would also expect that mention would be made of that in the ATSB summary.