This is notable on several levels. For one thing, Giuliani's behavior, like so much else, has been always been a matter of public record, and has been roundly ignored for months.
Mainstream media coverage has been sparse. The media would rather cover really substantive topics, like which candidate smells the best. You would think this would be a bit of a big deal, but it isn't, because the media would rather stick to the benevolent demi-god narrative that they've been spinning out about Giuliani, despite all the facts against him, ever since he entered this race, and really ever since 9/11.
The Giuliani camp has since said, by way of explanation, that Giuliani didn't want to join ISG because he was afraid it would become a "political football," and because he was considering running for elective office. As others have noted, this doesn't hold water. Giuliani told the Associated Press that he was considering a run several months before agreeing to join the ISG. And he quit the ISG after he was told to either start attending meetings or else quit the group.
It was a bad move politically for Giuliani to play hookie on the ISG in favor of raking in piles of dough for 'inspirational' speeches, but the real shame, as Steve Benen points out, is that Giuliani missed a golden opportunity to learn what the hell he's talking about: "Just last week, asked about the future of the policy in Iraq, Giuliani said, 'Iraq may get better; Iraq may get worse. We may be successful in Iraq; we may not be. I don’t know the answer to that. That’s in the hands of other people.'"
Giuliani had a chance to become something of an expert on Iraq. In a presidential campaign, he could have had real experience to point to. Instead he gave vapid speeches for big bucks.
This is sort of a side issue, but Giuliani's friend Bernie Kerik, lately convicted of ethics violations and ordered to pay $200k, reportedly said that he "couldn't afford to be here" (in Iraq as police commissioner) because he was raking in money speaking about 9/11 for Giuliani's slush fund, pardon me, "consulting firm.'" Rajiv Chandrasekaran's book reports that Kerik did nothing as police commissioner other than issue rosy, false reports about the state of the police force and wait to return to the States to continue cashing in on 9/11 (that, and start a vigilante Iraqi force, which he then failed to supervise).
So when people like Giuliani and Kerik say that "9/11 changed everything'" we know they mean it, but we also know that the change they're referring to isn't a "time to buckle down and really serve the country" sort of change; it's more like cash in quick before the magic wears off. Actually, that could be the motto of Giuliani's presidential campaign.