...Usually the preview is made half way through the film so people see a variety...
On Fox Movie channel or some channel, they had this commentary thing (it's like a long commercial thing) of 28 Weeks later (not days, weeks :o) of the beginning of it. They saw the beginning is set in the time of 28 days later, where this guy and others hideout in a building. A boy, who has been chased by people with Rage, and still is, come and begs them to let him in. They let him in, but the people chasing him find them all. The wife of, when I assume, is the main character is left in the house unable to get out while the husband cries while running from the people with rage who come from over a hill and some who didn't go inside the house.
My point is, beginning previews can be AWESOME >:D