Weird personal questions reported on checkin with airline

Cory Doctorow, author of the popular website BoingBoing, has a post on his site about a weird experience he had checking in for a flight from the UK to the USA. The airline required him to provide a list of all the folks he'd be staying with in the US. Not content to comply, he refused, questioned their authority to ask this information and, finally, has written an open letter to the airline, which is available here. This is the first I've heard of such questioning.

Boing Boing: Why is American Airlines gathering written dossiers on fliers' friends?

"Last week on a trip from London to the US, American Airlines demanded that I write out a list of the names and addresses of all the friends I would be staying with in the USA. They claimed that this was due to a TSA regulation, but refused to state which regulation required them to gather this information, nor what they would do with it once they'd gathered it. I raised a stink, and was eventually told that I wouldn't have to give them the requested dossier because I was a Platinum AAdvantage Card holder (e.g., because I fly frequently with AA). I have written an open letter to AA asking for details on this -- see the link below for the whole text...."