Sitewide + footer = greatly reduced in value at best.
Just want to give a little more background into the underlying reasons that result in the above described outcome of reduced value.
Regarding sitewides, it's Google's way of balancing out those links so they do not send out an inordinate amount of influence relative to how important the citation is. A sitewide blog roll link is not more important than the content found on every page of the site, particularly a link citation in the context of an article. So Google is trying to balance out the value of that blogroll citation so that it is more in line with Google's goal of crediting a link with the appropriate amount of importance.
Regarding footer links, that's a depreciation of the link due to it's location (bottom of the page) inferring lesser importance.
Put it all together and you get what Sgt_Kickaxe wisely stated.