A demo file is not the same as a video.
It records all the happenings on a given server at a given time.
This means that you can change what you're looking at, and from what angle, and at what distance, at any time during the replay of the demo. There is not a simple video format for this.
However, what it does mean is that you can get yourself a good desktop video recorder (I'm hearing a lot of good things about Fraps) and record a video of the demo from really good angles (though it may take a while to find these good angles).
In fact, you could record several videos of a single event from several different angles just to show how uber l33t your headshot was. :-P
It records all the happenings on a given server at a given time.
This means that you can change what you're looking at, and from what angle, and at what distance, at any time during the replay of the demo. There is not a simple video format for this.
However, what it does mean is that you can get yourself a good desktop video recorder (I'm hearing a lot of good things about Fraps) and record a video of the demo from really good angles (though it may take a while to find these good angles).
In fact, you could record several videos of a single event from several different angles just to show how uber l33t your headshot was. :-P