I can't see an immediate benefit from this for them, hence no motive.
I seriously doubt this was ever what Google set out to do but the examples given of how this would play down on the webmaster forum are eye opening. A quick 4 minute read.
Google’s examples clearly show a followed link. More importantly, new research indicates that verification is only possible if the link is followed. This makes sense, of course, because an unfollowed link might be put on a site via comment or forum spam. But this begs the question why a link was ever a decent method of verification in the first place. The answer to that question, of course, lies in the end result – over 1.7 million unique backlinks
Bob has been actively involved with online marketing since 2005 but got online in the late 90s. The first website he ever visited on his then brand-new Windows 95 PC was nasa.gov and he had no clue how to find stuff other then dig through DMOZ or use altavista.com The Internet was a much smaller place back then and finding stuff was relatively easy. Having a passion for technology and a background in IT, he spent several years running IRC networks and playing around with UNIX and Linux boxes for SETI and other geeky stuff. His professional career includes employers such as Dell and HP.
The commercial aspect of the web became clear to Bob when he started blogging in 2005 and getting paid for it. A couple of years and several website sales later, he started freelancing for small and medium size businesses where he’d help them to get onto the front page of Google.
Fast forward to present day; Bob is still helping businesses attract visitors from the web and making sure that the Internet gets a little bit better every time he works with a client. His greatest passion is educating people and showing them the commercial potential of the web.
He has been published on some of the largest industry websites such as moz.com and searchenginejournal.com and is a member of the Australian School of Management’s course advisory committee for Digital Studies. His online marketing skills and SEO expertise have been called upon by institutions and universities such as Curtin University in Perth and is also often quoted and cited as an SEO expert by online marketing bloggers around the world.