Well, I've just had one of my sites targeted for Negative SEO and it worked. Here's how it works:
My site was #1 for a money term on a medium tail keyword. Let's say "blue widgets for websites"
The #2 site is a very big player with a HUGE SEO buget.
The pages that rank look something like this:mysite.com/widgets/blue-widgetsbigplayer.com/widgets/blue-widgets
My site is all about widgets while bigplayer.com
is about a broarder category and has thousands of keywords and hundreds of thousands of pages. They rank #1 for things like "websites". We are smaller but more niche so have a lot more relevance about "blue widgets".
My site drops from #1 to #3 overnight for the keyword "blue widgets for websites" But this was the only keyword to go down out about 50 minitored. Nothing changed with the links nothing changed with the pages.
So I look at the backlinks and see A LOT of really low quality anchor text spam links going directly to mysite.com/widgets/blue-widgets.
This is the only page targeted by these exact anchor spammy keyword anchor text links. Spam anchor text was exactly "blue widgets for websites"
So someone is paying to hit a page for which I'm number one to take me down and guess who's number one now?bigplayer.com/widgets/blue-widgets
These guys are known for spending lots of money on paid links so what is cheaper? Buying / building links to overtake competitors or getting really spammy links to competitor subpages (which are unprotected) to take them out?
These low quality spammy links are much much cheaper. And you can't protect all your subpages from this stuff.
It's now more effective for the big players to invest in super cheap ultra crappy links to their competitors wherever they might be 2nd or 3rd on medium tail terms where there's no way their competitor's subpages will have strong backlink profiles to prevent damage from happening.
By allowing spammy links to hurt pages Google has unleashed a monster.
Plus you can automate this kind of stuff so it scales. Really ugly stuff and a sad day for SEO