The central issue here is trust. If you trust the provider of the url to maintain the link, ensure that it stays alive and pointed to what you expect, then it's

The central issue here is trust. If you trust the provider of the url to maintain the link, ensure that it stays alive and pointed to what you expect, then it's fine. How can that ever be a realistic expectation over anything but the immediate and short term? Not to mention that in the overwhelming majority of cases the "provider" of a URL is not the party responsible for maintaining it. I have to agree with the parent - unless the recipient of the URL [continuously] validates the source, she is simply asking for trouble down the road.