I couldn't imagine a better way to describe the current concept of grassroots marketing. Spam, and frankly heavy-handed and bad ways to resolve it (no links get traction, etc) have effectively closed the door here.

Anti-spam teams for a lot of social companies are under the umbrella of customer experience, and considered a cost center. The goal quickly becomes: be a hammer.

The impact to user experience, specifically around casual discovery has been profound.