I was able to track the person back through 4 machines and the trail went dry... and this was in the late 90s.
Do you honestly think its gotten easier?
My honest guess is *AT LEAST* 10 machines between... each compromised to not have trackable logs or anything usable to get to them.
its just not doable anymore.
Plus, more than likely its all scripted. machines going to machines to machines to machines to machines to machines to machines, all coordinated through IRC Chatrooms that have ZERO LOGS.