By referrer-filtering I mean that the site which hosts the image (i.e. in this case Flickr) would look at the site which was using the image (i.e. craftbrewing.ca) and either replace the image with an "oi, stop that" image, or just not allow it to be downloaded.
Dave's issue was not that... he was using links to HTML (i.e. a web-page) instead of a link to a picture, like say a .jpg or a .png.
I might be able to put a custom tag in for Flickr URLs -- i.e. so that the form Dave used would be fine, if it becomes an issue (happens again). It would mean having to use a new Flickr button instead of the Img button (in the post editor thing).
There are some WYSIWYG editors for BBCode but I've not had a chance to scope them out (and their usefulness in PHPBB -- this forum software). If anyone feels like doing the legwork to recommend one and it looks solid, I'll install it.