A partial answer:

Jonah,
I thought the same thing as you about why Gov. Blanco got off so easy. But then it occurred to me that she was in front of the Senate Finance committee, asking for money to get on and rebuild, and not before the House committee that was investigating what went wrong. My theory — which may be wrong — is that the Finance committee offered her an invitation to make a brief statement in response to Michael Brown’s testimony as a professional courtesy, since it has been all over the news, rather than because they needed to reconstruct any timeline. And that she chose to focus her efforts on making a case for the finances Louisiana needs now, rather than muddying the waters, so to speak, with a rehash of the past — which she is saving for another time (I’m assuming she’ll have to eventually appear before the House committee.) Read the following in that light and see if that makes sense:
Louisiana Gov. Kathleen Babineaux Blanco, blamed by the former leader of the Federal Emergency Management Agency and New Orleans Mayor C. Ray Nagin for many of the city’s post-hurricane problems, was given no questions about her response to Hurricane Katrina when she appeared before a Senate committee to plead for more federal money. She asked not to be questioned about it and the senators agreed. Mrs. Blanco, a Democrat, was invited by the Senate Finance Committee to respond to charges by former FEMA Director Michael D. Brown, who the day before called Louisiana officials “dysfunctional” in handling the aftermath of Hurricane Katrina. “Today, I came really to talk about job creation,” she said. Later, she told reporters, “The facts will speak for themselves. I will tell our story when the time is appropriate.”
Anyway, to quote Forrest Gump, “and that’s all I have to say about that.”