I contacted my lawyers about this one. Their reply:
Works created by Linking-In Images/video Found on Other Sites. When the image/video from another web site is incorporated into one's own page by means of an IMG/VIDEO link, there is no direct copying by the creator of the link. Nonetheless, when the visiting browser retrieves the image/video from the other web site and combines it with the text on the current page, the creator of the web site (you, Ricki) may be guilty of contributory copyright infringement for creating a derivative work. Consequently, one should not include links to images/video on another party's web site where copyright may be breached without first getting permission. The best practice would be to include only a link to the content on the other site, whereby your members would need to click that link to view the content.
If any linked image/video contains information that shows it is linked from another site, for example, the YouTube box that appears below embedded video, you should be able to allow that content. Inclusion of the linking details within the video should be sufficient to show viewers that the content is not stored on your site/server. Thus any request for removal should be directed to the hosting site, YouTube in this example.
From this, it seems members are able to post linked videos that display inside AP as long as the embedded video clearly shows that it is being linked, as the Vimeo and YouTube ones do.
So to clarify this thread, as long as you link your images/video in (with details of where they are linking from), it is not Ausphotography's (thus my) problem.
Be aware that someone may still contact YouTube/Vimeo etc regarding your video, and seek to have it removed from there, if you are using music without a license. Although it may not be commercial, you are publicly broadcasting the music without the relevant permission from the artist/creator