tedster - 2:41 pm on May 18, 2013 (gmt 0)
I've heard from a few people that this kind of thing started happening in March. It really isn't a total surprise - Google did talk about it earlier as something in the works. They apparently want to devalue and/or penalize any kind of PR-passing link that isn't a natural and freely given backlink.
In other words, if your site gave some value to the linking site, then I guess any link should be nofollow. Seems pretty harsh to me, especially if they are trying to do it by algorithm.