I just read a thing on theforce.net regarding the possible appearance of Qui-Gon in E2 and also about Qui-Gon's "non-disappearing act".
Uncle George says we will understand why this happened and is linked to Obi-Wan's statement about how if Vader struck him down he would become more powerful than Vader could ever imagine.
WHAT IF... Qui-Gon gave a "piece of himself" to Obi-Wan the same way Spock did the mind meld thing with McCoy just before he scarificed himself in ST2: TWoK? So now Obi-Wan will embody the spirit of Qui-Gon and it would be as if TWO spirits were acting as one.
I know, I know... it's pretty out there, but I'm just asking WHAT IF???
So don't don't go all Sith on me and goof on me or anything. I'm just putting this out there for discussion...