google is smart. If it sees a website linking to another on EVERY page, with the same anchor, url, etc... abviously it is going to know that you $BOUGHT$ the link, which is what google is trying to AVOID (webmasters buying links). In conclusion, sitewide links are EXPENSIVE and are not helpful, if not damaging. I hope this helps/
google penalizes only purchased links, sitewide or not. It doesnt matter. Also it penalizes sites with links to bad neighborhoods. everything else is just fine.
This is not accurate. Just because its a sitewide link does not mean it is paid. I've received numerous free sitewide links because other webmasters liked my content. And I thank them for that! Now if a sitewide link appears around many unrelated sitewide links, that may be damaging to the link seller. But in most cases the buyer risks only getting that link devalued.