Let's take a quick look at how Google has installed traffic monitoring systems all over the web, not unlike traffic cameras on the street, and they can collect enormous amounts of traffic information, probably the most extensive on the planet as they track across jurisdictions, networks, borders without any hindrance whatsoever.
Everything Google does is quite literally just another traffic monitor and they offer up all sorts of free stuff that webmasters and users alike greedily grab and stick on sites. What the webmasters and users don't realize is that all this free stuff gives them the power of knowing everything happening on the web although it seems benign in the beginning.
Think of Google's offerings as seismic monitors but instead of tracking tremors they track traffic on the web. Just like the USGS, they've installed a shitload of seismic monitors so they can track the slightest movement of traffic. Maybe more importantly for our discussion, they also track the lack of traffic which I'll explain later.
Examine some of the traffic tracking sources:
- Google Search: Google knows how you got there and they track where you went when you leave
- Google Analytics: By offering webmasters an invaluable traffic tracking tool Google also has access to everyone coming and going from your site and they know how they got there.
- AdSense: Publishers and Google both earn money but Google also gets the same data they would from Google Analytics for all pages with AdSense so it's a traffic data goldmine
- Blogger: Offering publishers a free place to publish also gives Google yet more traffic data mining opportunities
- YouTube: More of a destination than a traffic tracker, but people following links, viewing embedded videos, etc. are providing even more traffic data albeit somewhat expensive
- Google+: Blogger on steroids and those G+ buttons all over the place are just more traffic monitors.
- Google Maps: Embedded maps on virtually every About or Directions page on the planet tracking traffic.
- Various other products, APIs, etc. all contribute to the total.
This is why you should really fear Google's capabilities because neither Yahoo nor Bing had the foresight to create such a massive traffic monitor with programs like AdSense and Analytics so now those search engines are incapable of making the same kinds of changes to their index because they simply don't have the traffic data therefore they are still open to being gamed with link buying schemes. Perhaps if YPN! had been successful, or any of them had the foresight to offer free analytics, but the truth is Google has outsmarted the competition, the webmasters and the users as they are so entrenched at this point extrication could be impossible.
Just think of all those pages out there with AdSense, Analytics, embedded YouTube, G+ buttons, embedded maps, so on and so forth all collecting traffic data 24/7/365.
Google knows if those pages where your backlinks reside generate traffic or not, they know how to value links from those pages, and more importantly, if your site shows up on those pages they can look at everywhere else your site shows up and unravel the entire link building network. Compare all the sites that show up on the same pages and devalue them as well. Suddenly, the whole thing unravels like a puff of wind hitting a house of cards.
Don't think they aren't doing this very thing as Panda and Penguin are evidence it's happening.
To complete the comedy, Google gave webmasters a disavow tool so you can help them pinpoint locations that they weren't sure about and it probably outs everyone else that buys links from those disavowed sites. I can't even fathom what goes through the minds of anyone using that disavow tool. It can't be anything intelligent or they'd avoid it like it was flesh eating bacteria. Disavow reminds me of McCarthyism (MattCuttsyism?) and how people were suddenly eager to turn on their neighbors and claim they were communist just to save their own asses. Disavow.
My bottom line is don't put your links in places designed just to pass PR as I'm pretty sure those days are over and if they aren't, they soon will be because it's simple data analysis to find these shady places. Not because of what they do, because of what they don't do, they don't send visitors anywhere.
While I don't know how smart the boys at Bing are, but it would seem they could extrapolate some good information from the sudden changes in the link graph and figure out which sites Google has exposed. If that happens, which is very possible with just a little analysis, link schemes could also be easily devalued in Bing and Yahoo as well, assuming they're smart enough to identify the sites.
Think about it and link responsibly because Google is watching and Bing may be as well.