The Daily Kos has a story, and links to one from the AP, in which American citizens were removed from a town-hall meeting to tout Bush's plan to eliminate Social Security. Many stories about came out about people removed from Bush's campaign stops during the last presidential election, but this is different.
Given that these are taxpayer-funded events, they should be open to all taxpayers who obtain tickets appropriately. (The people removed from this event received tickets from their congressional representative.) The events have become publicly funded private events. By controlling who can participate, the administration silencing those they disagree with, or more likely fear.
Controlling information is a key to controlling people. It's worked through history, and it appears to be working in the US.
Joseph Goebbels would be proud.