With "wetware" on the rise, and with the recent passing of Leslie Nielsen, I think this is an appropriate time to remind people of the movie Forbidden Planet. Besides being one of Nielsen's few (old!) bits of "serious" acting, the movie has an interesting point: computer interfaces must distinguish between unconscious thoughts and purposeful instructions. Otherwise the machine will start executing instructions directly from the subconscious ("id") whether you really wanted to do those things or not.
Well of course I expect people to examine the idea critically instead of lifting it straight from a 1956 movie and applying it to next-gen interaction design problems. It's just an idea I think people should consider.
http://en.wikipedia.org/wiki/Forbidden_Planet