Spam objects are attempts at deliberately misleading search engines, and there is also a lot of text that misleads readers. Sites with untrue statements, misleading medical claims, and information that was once (considered to be) correct but is now out of date. The issue of document quality or accuracy has not been researched much in web search or information retrieval contexts. Relevance, yes, quality, no. And it is essential for generating satisfying search results for searchers.