Since the 9/11 Commission was able to have months and months of mostly open hearings into all matters regarding intelligence and covert operations, I see very little reason why Able Danger, which relied on open sources and is said to not contain anything that would hurt national security, should not be similarly discussed in open hearings.
Some testimony may well be better suited to closed hearings, and that will be determined as questions are submitted, not determined in advance to the simple questions like:
1) Was Atta identified pre 9/11.
2) If yes, who was told about it/him and what was done.
There is no way that the answer to those two most pressing questions endangers national security. And since the AD guys have been on the airwaves for months now talking about these matters, I really don't see the problem.
Certainly the administration has my support and benefit of the doubt, but it's time they get out in front of an issue and play offense instead of their usual defense.