It seemed that not enough people wanted to watch Knight and Day in the US, despite it 'starring' Tom Cruise and Cameron Diaz. Or maybe because it has Tom Cruise and Cameron Diaz in it. Perhaps the idea of seeing famous people on screen has become less exciting than a big 3D-fest, franchise, or simply good films.The advertising for Knight and Day is just saying 'Look, shiny famous faces. We don't care if they're insane and/or boring'. So it's a good thing that it failed to make a billion dollars? It's definitely a slap in the (not so shiny) face for some suited studio people, but under all this is a film that's not bad. The absence of a negative. You won't remember it the next day, but never mind. Tom Cruise is a US agent gone mad and on the run from everyone. He's funny too, casually and amiably shooting everything while trying to keep Cameron Diaz calm. The expensive car chases and helicopter fights are no bother at all. He's definitely the best thing here, even if everyone seems to forget about the comedy halfway through. It starts to become a standard action film and everyone puts on their serious faces. Still ridiculous, just not funny. A shame, but it's still done well.
In some ways it's flimsy. Every now and then Cameron Diaz's character is drugged or knocked out, making the screen go black and fade into a new exotic location. A series of set-pieces with no link, like levels in a game. A lot of action films travel rapidly travel around locations, but not usually so shamelessly. Doesn't really matter though, in much the same way as you ignore Diaz's habit of talking out loud when she's deducing things. It'll do.