One of my coworkers was heading to Guatemala for some mission work. He flew from Toronto, with a layover in Atlanta. When he went to get on the plane in Atlanta, he pulled his boarding pass out of his passport and the first page of his passport came with it! They wouldn't let him get on the plane because they weren't sure he'd be able to get back out of Guatemala.
He tried the Canadian Embassy but since it was a Saturday, he couldn't do anything until Monday AND it would take a couple of weeks to get a new passport. He was able to get a flight to Buffalo - as long as he wasn't crossing a border, he didn't need his passport. But missed the last bus to Toronto so had to rent a car. All told, including the fees for getting a new passport and expediting it, it cost him about $1300.
So word to the wise: if you put your boarding pass in your passport, be careful when you pull out the boarding pass. Or better yet, put it at the back of the passport. Apparently, they wouldn't have cared if it was just one of the stamping pages that got torn out. But because it was the page with his picture and all the info, no dice.