The questioning of this kind is idiotic. You get so many false positives that you can only do this where you don't have a lot of traffic. For example a lot of colleagues who fly a lot have NO idea how far the hotel is from the place they're working as they cab everywhere and don't pay attention, the best they could do it say it cost me 20 dollars to get a cab. Lots of people are nervous about flying, immigration and security anyway so being flustered, stammering or getting things mixed up is not an unlikely occurance. I've seen people harassed at airports for forgetting the hotel they stayed at, and this is only going to get worse if they can be denied a flight for getting things wrong. Finally, I am one of the people who throws reciepts etc away when I pack my bags (unless they're needed for expenses) so I'd rarely be able to prove I'd stayed in hotel X, eaten at restaurant Y or been in cab Z which gets you extra attention.

I'm not saying that intelligent questioning doesn't have a place, but once you start to do it, say, at ORD or LAX on a busy holiday weekend, you're going to back up the queues and cause huge delays for everyone. Given the fact that babies are being given a hard time because they appear on no-fly lists, I have no faith that these could be implemented in the US in a useful fashion.