Hi, I have had in the back of my head this thing that sitewide links are no good, that they seem artificial - and therefore one might get penalized for them, or at least not get the value of a normal link. It all makes a bit of sense if you only consider footer links, but thinking about it, it seems completely bonkers if you consider blogroll links. So what is the truth? Are sitewide links bad or are they maybe just as good as any other links?
I think if they are overdone in your backlink profile then I would be concerned. Diversity is the key to long life on the internet (read: link equity)
But I don't see any reason to be too concerned since half the blogs on this planet link in ridiculously long blogroll links, often 'incestuously to their own network websites, and don't seem to suffer many problems.
As BeeDeeDubbleU indicated, I have never really seen any negative effects from such links. While site-wide links may be discounted somewhat, they still seem to carry more weight than a single link. I've seen such links used very effectively with sites large and small.