Well you can but you need to stop thinking like you are shooting a video camera. Other then a couple of quick shoots at the beginning there is no (or very little zooming. They are using prime lenses and you better have fast lenses to shoot inside weddings where you have no control over the lighting. Also most of the camera movement is a steadicam.
The thing is you cannot shoot like video, you have to shoot like film, camera moves and zooms are used to reframe for the most part. You can do a little zoom but not like a video camera, for one thing you don’t have the zoom range, video have 10-20x zooms, DSLR quality zooms are normally no more than 3x.
[Sohrab Sandhu] “If they can do it why can’t I ? “
No reason at all, but get ready to spend some bucks on gearing up a DSLR to make it work. The cheapest thing is the camera, but to make it work you have to spend the $$. NOt trying to say you cannot do it but to make sure you are looking in the right places. Like I said, there are no zooms faster than f2.8 and each will set you back at least a grand or two.
There are several companies that are doing this level of weddings, they are awesome, and they are getting a good fee, there weddings start at $6000.