Consensus on sitewide links

I've read a lot of conflicting information on site-wide links both for and against them. I've read reports that GoDaddy manipulated them with great success by placing badges on peoples' websites but I'm also aware what works for an authority site may not for a micro site. Word from Google is that site-wide links are often discounted or pass very little link juice at all but I'm aware this may just be the usual 'guest blogging is dead' propaganda.

Normally I discount sitewide links when I'm evaluating a PBN domain because I've always erred on the site of caution, plus they inflate metrics. Today though I came across a domain with a sitewide link from a large authority site with >80,000 pages all linking to the site, which is the only thing that the domain has going for it. I'm tempted to buy the domain to use as a 301 but if it's passable as a regular PBN I'd prefer to use it that way.

What have other people found with site-wide links?