We posted about the requirement to link Google AdSense accounts with a Google Account in February. As indicated in the comments of that blog post, the frustration of doing so is still there and a lot of publishers are not taking the plunge as a result.
Well, Google is reminding you that you have no choice. You'll need to do it, according to a Google Groups thread. AdSensePro Ashley refers to a new post on the Inside AdSense blog which states that if you don't make the change, you'll be locked out of your account -- for good. (Roger, I'm sorry.)
There's no exact date for when this will be rolled out, but Google states that it will be a requirement "in the next few weeks."
Forum discussion continues at Google Groups.