Scribd ceased doing related search queries some time ago.  Their CEO described it, to Techcrunch, as "reducing the aggressiveness of our SEO, which reduces total traffic in the near term but increases the relevancy of Scribd links in search engine results."<p>Scuttlebutt among SEOs whose opinion I respect suggests that it is highly probable they got a backchannel from Google telling them that either they could drastically reduce the footprint of their pages in the SERPs or that Google's search quality team would assist them in doing so.<p>Anyhow, their traffic went down by about 50% in a month, if you trust Compete et al.<p>Search for [Scribd "aggressive SEO"] if you want the whole tale.