A while ago there was a discussion on the chat frequency regarding "ride reports" at 35W.
One poor soul was in moderate turbulence at 37000'. He was the only one experiencing any turbulence and it was suggested to him that it may be the wake from the preceeding a/c at 38000 (I seem to remember that vortecies descend at 500'/min so if you are 2 mins behind the preceeding a thousand above .....).
The responce was amazing, the chap suggested he had tried descending to 36500' and climbing to 37500' to try for a smoother ride!
For the next few minutes all hell broke loose (quite rightly) with numerous other a/c trying to find out who this idiot was. Never did find out who it was.