What are bad backlinks - as in a site would be better off without them? I can see that large amounts of spam in UGC, or links from link farms are bad, but what about these:
- Links from minor search engine SERPS? Does it matter whether the search engine is a real one (i.e. actually provides a useful service, such as a niche SE) or a scraper masquerading as an SE? Of course allowing SERPS to be crawled is bad practice, but some of these are strong sites.
- Site wide links (from your own sites, relevant sites, irrelevant sites, footer links from WP themes..)
- Scrapers (and what if they are banned? If they are not in the SERPS does that mean there is no effect?)