in my case i have a movie that borrows live webcam
images from elsewhere. i have no control over these
images, i just grab the urls for the jpegs and load
them on demand in my movie.
That is similar to framing someone else's content
on your site, or using RSS or similar technologies
to show outside content integrated in your site.
You can have expectations regarding to what will
appear as part of your work but the lack of control
can lead to unexpected results. Imagine a movie
that borrows landscapes from a series of webcams.
The one of the webcam owners decides to use her
cam to show off her naked body. That would alter
the content and the meaning of your movie - and
possibly make it very popular. :-)