This is too bad. Most of the other SEO-spam tactics (paid links, affiliate networks, etc) were pretty clearly destined to be spam traps and invite Google's wrath. Unfortunately, one of the things I thought was best about content marketing and guest blogging was that it encouraged founders and experts to find where the audience was that would appreciate their product, and create high quality content explaining why it mattered. Many have written about how founders can be tempted to stay in and wait for customers to come to them, but a guest blog could help bridge that gap, as they can stay in while still finding customers, and honing their message (plus the comments to these are often really valuable wells of feedback from people you may not have been able to reach before).

Here's hoping for a happy medium here.