I've been discussing this with peers recently and the general outcome was that for SEO purposes you should have your created and designed by links etc as links only on the homepage. Then for content pages (basically anything other than the homepage) you should remove the link as Google sees that as duplicate content.
Essentially it's detected as a spam-related link because there are lots of pages all with the same link back to another website. I haven't seen this done anywhere from memory and wanted some feedback as to what the general rule of thumb was when it comes to vanity links. Any answers are much appreciated, thanks.