Query Deserves Freshness(QDF) is a ranking factor used in Google Algorithm for time sensitive search phrases. For example, if you had searched for Steve Jobs when his death made news in October 5, you would have noticed websites constantly changing their rank in top 5 position for the term "Steve Jobs dead". This is because Google in 2007 started tweaking its algorithm to include fresh blog posts and news about hot topics in its Search Results page, moving away from listing traditional news sites as the only source for "hot" topics.
Initially this led to low quality sites ranking for hot topics, which was soon corrected by including 'Authoritative sites'' on the "hot topic" to rank for the search term. For example, when the news of Jobs death was hot, blog posts and main stream media posts began to rank in the first page, quickly changing its position, giving way to more authoritative sites on this topic like Apple, Reuters, Gizmodo, WSJ and PC World.
What is the value of Query Deserves Freshness?
The value of QDF is based on relevancy. If you are trying to game Google with a small blog post, 5-10 mins after an event, then you might rank in the top 5 position for the "hot topic". You might also get hundreds of visitors but the search results position would soon drop once authoritative websites on the hot topic starts publishing their posts. It is important to understand that QDF has low value if you are targeting topics, non-relevant to your website's core theme.
How has Social Media changed Query Deserve Freshness algorithm?
On Nov 4, 2011, Google announced that it will give preference to websites that update their pages regularly for time sensitive keywords. Social Media like Twitter and Facebook have transformed the speed with which information is spread among users. Since Google removed Twitter update from its search results in July 2011, users are now using search.twitter.com, Bing powered Facebook Search and Bing Social Search (bing.com/social) for real-time updates. 35% of Google's keywords are time sensitive searches. Stale posts about events would be replaced by regularly updated posts.