The data in Webmaster Tools has been historically unreliable[1][2]. If you compare it to data in Google Analytics, the two have often been world's apart. Sadly, this isn't going to come close to replacing accurate keyword data in GA.
"Don't link to other sites or you'll improve their ranking. Link to mine instead" is pretty much what this site is saying.
This is why Google created rel="nofollow"[1] and if you are really worried about where you pass PageRank to it is a much better alternative than linking to some random 3rd party site while passing value back to them.
Since the Panda update everybody should be using rel="nofollow" on all outbound links, otherwise you risk getting knocked back to page 100 should any of the sites you ever link to trip a flag that leads google to classify them as a spammer.
For what it's worth, there are many indications that using more than a few no-follow links on your website 1) hurts your SEO standing, and 2) still passes Link Juice to the external website (just slightly less than its do-follow counterpart).
This happened after Google discovered that people were abusing no-follow - by trying to hoard the website's weight and not sharing it with anybody.
You should definitely not rel="nofollow" all outbound links. Do it to sites that have a risk of becoming a spam site maybe, but a quality site usually doesn't become a spam site overnight and you'll do more harm than good to yourself adding by rel="nofollow" to every single outbound link. Google wants you to link out to quality sites so you don't need to nofollow those.
The most frustrating part of negative SEO or any link cleanup is that Google doesn't tell which links they think are spammy links. If you are working for/with a site that has been online for a while, they will have thousands of crappy looking links pointing to their site.
Scraper sites pick up content from other websites all the time and cross post with porn and other crap. Directory submissions that were perfectly fine 5 or 10 years ago can now be viewed as "low quality" by Google. Blogs that used to be well-maintained have been bought by spammers and SEOs and are now content farms.
Google's lack of transparency when it comes to links is very troublesome. I understand they can't give out the ins and outs of their algo, but asking your average website owner to go through 10k+ backlinks and identify and remove the links is a pretty tall task when there isn't a clear standard on what is bad and what isn't.
Google's WT index seems to provide a fair amount of the links. There are a few 3rd party tools that do a really good job of indexing nearly all of the backlinks to your site:
It's a real problem. I do SEO for a living and work with hundreds of sites at a large agency. I've seen several hit with negative SEO from competitors ordering link gigs on Fiverr or asking some low quality link provider on Digital Point to build 10,000 links in a short period of time.
This has killed rankings for a few sites that I've worked with. It is really easy to get thousands of spam/porn sites to link to a competitor with exact match anchor text for whatever keyword you want. And it's basically impossible to figure out which competitor is doing it to you.
Google used to just 'devalue' all crap links pointing to a site. A link could never hurt you. Now that links can hurt your site, it's totally wide open for this type of thing to happen.
The pendulum has definitely swung the other way. It is now much easier to kill competitors with black hat tactics than it is to promote a business with black hat tactics.
I remember a comment by Eric Schmidt that the best way to combat spam was through "brands". While brands are a component of good search results, I can't think of a more misguided philosophy. If the only advice Google has about where to buy something is to buy from "Amazon" then Google has lost its utility in revenue generating searches. I think the best way to combat SEO spam is through engineering and hard work. Giving all the power to established brands is a shortcut that will ultimately undermine Google's core value to its users.
That case study is truly frightening. People spend years of their lives and millions of dollars to get their sites to rank higher in search engines... and then this can happen.
While the markup doesn't do anything for SEO, Easter eggs like this are often created to help generate links back to the particular page from sites like HN...which can boost SEO.
The original submission title was probably tongue-in-cheek, but I'd bet the creator of the page had SEO in mind. Getting a ton of pg lovers who probably also link programming to link to a programming page on the site would be killer for SEO.
This is similar to creating a unique 404 error page that can generate tons of backlinks.
Some sophisticated SEO link spam for 'pay day loans'
Out of curiosity, I looked up that particular pay day loan site's backlink profile. They went from having zero websites linking to them to around 250,000 in the matter of a few hours. All of the links had anchor text with some variation of 'payday loans' or 'payday loans UK'
My guess is a lot of people are creating data visualizations for their own site/business and making the sets public without thinking of them being indexed and searchable. As I said, the documentation on this within Fusion Tables is pretty awful.
[1]http://www.portent.com/blog/analytics/google-webmaster-tools... [2]http://moz.com/blog/comparing-ranktracking-methods-browser-v...