This is a highly controversial topic, I was only 7 when this sad event happened, but over the years I went through many articles and books, and read both sides.
I came to the following conclusion:
Yes, maybe the USA did plan this with the Taliban, but:
(1) They did not expect this mess.
(2) They did not realise the amount of people they'll effect.
Bulono, you said they did this to invade Afghanistan. Why is this a bad thing? Afghanistan was completely ruled by the Taliban, and they did not give women their rights, and just treated them like pieces of furniture. After the invasion, then first lady, Laura Bush started a huge campaign to help these women. Joint with UK's PM Spouse then Cherie Blair they opened universities and encouraged education, and health in the country.
This in my opinion was a good thing!
On that morning, the first lady was on her way to the Kennedy library to give a speech, and the president was at a school. If they knew about it, why didn't they leave Washington? If they knew couldn't have they went on a state visit some where in Europe, and then come back? The fourth plane, flight 93, went down in a field in Pennsylvania after the passengers revolted. It was said that the plane would have hit the White House in Washington, the president and the first lady along with Condolisa Rice and the senior staff at the white house were underground, under the white house. If they knew why did they choose this place to hide?
If the sole purpose for this 'show' was to invade Afghanistan then it's unbelievable, no towers were blown up when Iraq invaded Kuwait in 1990, they were simply more powerful and thought Kuwait was part of Iraq, so they invaded us.
No buildings were blown up when George Bush invaded Iraq, or should I say freed Iraq, if he didn't Saddam Hussein would have still been alive, and with Iran's Ahmedi Nijad they could have created another Hitler!
As nid said, thousands of innocent people were killed, whether it was the US. who planned this out, or Osama Bin Ladin, thousands of families have lost a husband, a wife, a son, a daughter, no one was expecting to die on this morning, they were all heading to work, like they did every single day for the past years.
PS. everyone has a point to view, that's the reason for a debate, nothing has to leave this board.