Well, you know that us Canadians are responsible for letting the 9-11 terrorists into the US, don't you?
Oh, you mean the terrorists that we legally allowed into the country as students, but overstayed their visas? Yeah, the US has it all worked out...
After posting last night, I found a couple interesting things... In 2005 there were 660,480,345 airline passengers in the US. So suppose that there are 100 people a year that would really want to do harm to the US and would run a plane into the ground, that means 99.99998% of people traveling on planes are just normal people. I am assuming those that cross US borders would be of a similar situation.
The problem is that people who do want to do harm that would cross a border are going to try find ways to be as legitimate as possible. They are not going to check the box on the I-94 form that says they have been associated with a terrorist group. So we are going to make life difficult for the rest of us? On the other hand, showing a government issued ID at a border crossing does make sense, and there are 100's and 100's of currently "valid" IDs. It is much harder to weed out counterfeits, so condensing this down to passports, at least makes it a little bit better.