This is fairly old topic, but I just noticed something that may be interesting to others. I was having all sorts of trouble with phantom keys on my Macbook Pro (2010 model), both with and without noise cancellation, and I noticed that it only happens when I have the power cord plugged in to the laptop. Even in a dark room, I get phantom keypresses if power is connected. When I disconnect power (run on battery), I stop getting phantom keys even in a reasonably bright room.
I saw that it got better when I relocated my laptop to a different space earlier this week, but I didn't make the connection to the power supply until now.
Rob