We do a lot of video contests, and as a result, they have a very flexible and scalable video submission engine that we using within the applications.  They generally support video submissions via webcam, upload (most popular video formats), and link submission (YouTube, Vimeo, and more).

Video and Webcam Upload and Submission Dialog
When submitting a video, users can record directly from their webcams, upload a video file, or record it from their mobile device.

Entry Dialog
The entry dialog is used to collect information from the user submitting the video; fields can be required or optional.

Done Dialog
This dialog is displayed once the entry is received, and can be customize to include an additional call to action message (purchase item)

Submitting Links
We also support user submitted links for videos uploaded on services such as YouTube and Vimeo.

The entry and complete dialogs for this option are the same as for the video upload/webcam set of dialogs.