I was just watching TPM last night and this thought occured to me, and yes this has most likely been discussed in earlier threads/ posts but if you think about it, Vader is the result of Qui Gon Jinn and not Obi Wan Kenobi.
Think about it, Qui Gon insisted that the boy be trained that he is the chosen one, even after the rest of the council sided against Anakin's training. Because of this the fate of the galaxy was sealed and Palpatine's plan came into being. If Qui Gon had ignored the boy and never bought his freedom from Watto, Anakin would still be a slave and Vader would never be.
As far as Obi Wan fault's (as he states in ROTJ, "I thought I could instruct just as well as Yoda, I was wrong.") Obi Wan was only granting a dying Qui Gon's last wish that he train Anakin. And since Obi Wan became stubborn at the end of TPM (" Master Yoda, I gave Qui Gon my word, I will Anakin, without the council's approval if I must.") the fault later would fall upon Obi Wan feeling guilt that he as well do not listen to the council.
"Clouded this boy's future is" a message from Yoda that should have been taken more seriously perhaps. Could it have been that Yoda might have been the only member of the council that could see through the Dark Lord's plot?