Like with many other burning SEO questions, there is no definitive answer as to whether sitewide links are good or bad. If we for just a second forget about search engines, we will see that, on the one hand, sitewides can be good for very important links (as users are much more likely to click them), besides they make the overall site template look more consistent (encouraging users to feel more secure).

On the other hand, because of them the site might lack diversity (getting bored with one and the same content throughout the site, the visitors might want to leave soon). Now, when talking about SEO, the usage of sitewide links may also be highly controversial: