I have seen many websites got ranking suffered by down from the first page to 10+ page. I have inspect them and found most of them has sitewide links as their main link profile. Do you think Google is completely devalued sitewide links? Do you think sitewide link should still be a part of link strategy?
what do you mean by sitewide links as their main link profile? Are you talking about the sudden drop in traffic for a lot of site on the 21st of october?
not really. once the link stays as sitewide in a trusted site google will absolutely won't devalue it.
The sitewide link is the link that appear at every single page on a certain website, mostly are blogs. It could be at "sidebar" or "footer".
Well it's strange because I have two nearly identical sites, only one in french one in english, the french one was getting more traffic and has been hit, the second one didn't get hit by the 21st october drop in traffic. Both have sitewide links on them linking to different sites (sites in the language of the site)
I believe there is a percentage of blog sitewide links you can have of the total amount of backlinks. If your percentage is higher than your site might look suspicious for Google
Thai is what I am thinking. Many websites I have inspected have too high ratio around 70% of their link profile as sitewide links. It is a hard to guess the "proper percentage" of sitewide links that website can have without got penalized because of over-optimized.
Now that you mention it it's true that the french site (the one who got punished on 21st october) has mostly links from my other sites (sitewide links) whereas the english site has a lot of links from my referral program, so from many different places owned by my members.
I have websites with sitewide links and the do very well so I don't think there is a issue with sitewide links.