They didn't loose the battle. They capitulated without even trying. God knows why. I can't imagine they actually think ruining their own product increases their revenue.
It'd be trivial for them to remove/derank 99% of spam by manually reviewing search results (still at negligible cost) possibly letting users flag results for them for guidance.
Example: Is a page copying lots of text from stack overflow? Then it's probably spam! Don't show it on the first page of the search results!
How do we know it is the page that copied from SO and not the other way around? If they let users flag, SEO people will figure out how to flag themselves for their benefits
That's where the manual review comes in.
Is it reasonable to assume a seo spam site has produced content stack overflow content, that stack overflow then copied to their page? No.
It'd be trivial for them to remove/derank 99% of spam by manually reviewing search results (still at negligible cost) possibly letting users flag results for them for guidance.
Example: Is a page copying lots of text from stack overflow? Then it's probably spam! Don't show it on the first page of the search results!