Stackoverflow: "One of our major performance optimizations for the “related questions” query is removing the top 10,000 most common English dictionary words (as determined by Google search) before submitting the query to the SQL Server 2008 full text engine. It’s shocking how little is left of most posts once you remove the top 10k English dictionary words. This helps limit and narrow the returned results, which makes the query dramatically faster."
^Luhn, H. P. Keyword-in-Context Index for Technical Literature (KWIC Index). American Documentation (Yorktown Heights, NY: International Business Machines Corp.). 1959, 11 (4): 288–295. doi:10.1002/asi.5090110403.