In The Phantom Menace, Qui-Gon is looking for a way to obtain the parts to repair the queen's ship. He discovers that junkdealers have a weakness: Gambling on pod races. Then he states:
Qui-Gon Jinn: Greed can be a very powerful ally.
And he really do take advantage of it, instigating it on Watto several times...
Later, on Revenge of the Sith, Yoda is giving advice to Anakin, who is troubled by Force visions of his wife dying. Yoda then warns him:
Yoda: Careful you must be when sensing the future Anakin. The fear of loss is a path to the dark side.
Attachment leads to jealousy. The shadow of greed that is.
So, greed, the same ally so well used by Master Qui-Gon, is also a quick path to the dark side.
Isn't it a counter-sense? Wasn't Qui-gon flirting with the dark side by doing so?