Confidentiality of sources is a real social and professional convention -- and one of its boundaries lies in a source providing a release to a journalist from any promise of confidentiality.  When both parties mutually recognize that it ends, that's it.

So, why doesn't Bob write the story?

The more important question might lie in Woodward's silence for two years, even with his Senior Editor, over what he knew.  His denial that he knew anything important on Larry King; his dismissive and angry characterizations of Fitzgerald and the Plame investigation ("they won't find anything"; Fitzgerald, "a junkyard dog") -- none of this behavior fits with his present denials and carefully parsed, incomplete explanation.

Woodward is among the most wired-in and connected journalists in Washington. The real story around Wilson-Plame wasn't Judy Miller's 'principled stand' over a confidential source, but the manipulations and outright lies by a dangerously improvisational government.

All of that pulled America into a war with the true purpose of advancing a necon strategy of endless American hegemony; Wilson got in the way, and had to be taught a lesson, Bush-Cheney-Rove style -- and that was a loose thread which could unravel the story.

Woodward had to know he had been given a glimpse into a political underworld even worse than Watergate. Any other reporter on the planet would love to be handed such an opportunity.

What were Woodward's priorities? Why did he focus instead on the drama around Miller? Why did he denigrate the investigation, and its chief investigator? Why did he ask his friend Pinkus to "leave him out of the reporting" in a story Pinkus would write? Why didn't he pursue the story?

Why?

I think the answer re: Woodward is easy: he's an elite. In the club. His life depends on access, and he won't lose that. (There are books to write, dammit.)

Woodward in the 70s was an outsider, willing to take on the Institution.

Now he is the Institution.

What's more troubling to me is Pincus, and why he remained silent (even to the Eds.).

I think we can narrow down the source to handful of people from what Woodward is said.  He was not sure that this person had testified to Fitzgerald before, so presumeably it has to be someone who has not been publicly identified as a witness.  Also, we it is someone who is less concerned about legal implications than the impact of having this made public, suggesting someone in a visible or public relations role.  Eliminating those who have issued denials at being the source, I would say this leaves:  Condi Rice, Karen Hughes, Richard Armitage, and possibly Stephen Hadley (who refuses to confirm or deny).  I think all but Armitage were part of the WHIG group from which this originated, and I would guess that it was someone from that group.  Karen Hughes would make as a PR person with contacts in the press as would Hadley because he could speak with authoirty on intelligence matters.