I do appreciate all your posts - and especially the responses that speak directly to the question of whether a site wide link is more or less effective,
PR-wise, than a home page only.
Of course I have gotten many clients from those links, and even more leads that I have to turn down as competitors find my client sites high in SERPs and want the same 'magic.'
I don't agree that it's an unethical practice or irrelevant. There can be nothing ethically wrong with receiving credit for my work when a client has agreed to it. And a no follow would not be appropriate; the link is not paid. It *is* a vote of gratitude from a client to the contractor. No different than credits on movies, in a book, or anywhere else where a designer or author has worked on a project and the credit is part of the arrangement.
On relevance: I have no doubt that search engines know that a link to a web designer or
SEO in the footer is directly related to the design or optimization of the site. Nothing could be
more relevant. It's a sample of work done in one's field! That's like saying a signature on a painting isn't relevant.
As to the link that remains after to haunt me ... for the relatively few clients who have left, I have usually removed the link before I relinquished control over the site. With the few I haven't, I haven't had any sort of issue like that in 10 years in the business. Just not the sort of thing I attract, I guess.
I still wonder,
PR-wise, whether a home page only link would be stronger. My interest is more academic than likely to become practical. I really don't have time to go back and change them all anyway, but I do think this is an interesting question and look forward to hearing more from other designers and SEOs on this.
Thanks to all, MJ