if it were not a dark side thing, then more jedi would know about it. the jedi have been around for over 10,000 years, and NONE of them know about a ghost trick. all of a sudden, the sith reappear, and suddenly youve got ghosts. add to that the fact that dooku has a connection to qui-gon, and at one time, was a good jedi. And I really dont think Palpatine and Dooku are in cohoots as much as we might think at this moment. Dooku is probably not stupid enough to let Palpatine completely use him. I think when Dooku realizes what Palpatine is REALLY up too, he switches sides. While that IS totally speculation, there is no other way to explain why no other jedi know about the ghost trick, if its not connected to the sith. and Dooku is the only sith who has the possiblity of turning good.
there is also the fact that every time a jedi dissapears as a ghost, he does so in the presense of the dark side vergence in the force.
obiwan w/ darth vader
yoda near the dark side cave
anakin w/ the presense of the dead emperor, or simply the fact that he he is the chosen one, who is very strong with the dark side.
its got nothing to do with the darkside, there is no darkside cave (officially) its got to do with Luke and their being no Jedi left to train him so they have to come as ghosts to help him. it might even be as simple as the sw's films are pretty much based around Luke and so the film is seen from his point of view, hence we see his ghosts and no elses. Thats the reason we don't see qgj's ghost, tpm is too generalised to be based around one character, ot is not.
I like the idea of Dooku turning to the goodside to defeat palpatine only to have anakin/vader beat him, nice twist.
I think if Qui Gon was going to be a ghost it would be in ep2 not 3, too long too wait, (15 years plus), i like the idea of him being a hologram or in a video with dooku, nice plot twist.
This ghost thing falls apart when you look at the sith, they have jedi training and yet there is not one sith seen as a ghost, i would like to see darth bane appear in ep3 but i'm doubtful.
surely palpatine being all powerful could come as a ghost???
ok, sand person, your idea that there are more ghosts but we just dont see them kind of falls apart when you take into account that in the OT, it is clear that vader doesnt know obiwan turned into a ghost, or even that it is a possibility.
as to ush's comment about a vergence, he is correct, we really dont know what that term means. im going to start a thread about that...