If the event winds up being a 2 hour barrage of questions about the NSA, it might be redeemed.
Do you actually think the DNC or the President's staff would allow that to happen? This isn't a dig at the Democrats, either--I can't imagine the RNC allowing a fundraiser dinner to become a town hall meeting to grill the President on a controversial issue.
There was an article in the NYT Sunday Magazine yesterday which had VP Biden being put on the hot seat by gay marriage supporters[1]; I would hope that the NSA's mass data collection practices, which are much less controversial (they are widely unpopular, unproductive, and give terrible power to any bad actors who have access), would be as worthy of questioning.
EDIT: If the event winds up being a 2 hour barrage of questions about the NSA, it might be redeemed.