When building links what counts most in terms of link juice is the number of links you are getting from different IP addresses. That said is there much point in having a sitewide link? For example a homepage blogroll link from one website counts as one link. If that site has 100 pages you end up with 100 links if your link is sitewide but Google is likely to discount 99 of these because they are from from the same IP address. Hence the question is there any point in having a sitewide link? In fact I wonder if having a sitewide link could have a negative effect. Any thoughts on this?
site wide links can help but it is better to get links from different domain. a good thing about sitewide links from blogs is that every new post in this blog will link to your site so google will crawl your site everytime the blog is updated.