This just shows how seriously Google and Co take PR (or Link Poularity) manipulation nowadays.

Google has always preached "Design your Pages for Visitors not Search Engines", now that same philosophy is being applied to links. By that, I mean they want you to link to another site because it is "Likely" to be of some interest to YOUR visitors, not because you want to manipulate PR.

I predict this is the first of many measures that will be invoked to try and restore some credibility (and usefulness) to the value of PR as a Yardstick and hence improve the declining standards of SERPs relevence by those Search Engines that use it to evalate relevency.