Highlights from an article about procedure changes to assist Federal Air Marshals (important: not made for your convenience or safety):

“the mix-ups, in which marshals are mistaken for terrorism suspects who share the same names, have gone on for years—just as they have for thousands of members of the traveling public.”
“one major air carrier reports roughly 9,000 false positive hits on the watch list every day”
“The Terrorist Screening Center announced April 10 it will automatically review nearly 500,000 names on its watch list that are frequently matched during airport screenings and other law-enforcement encounters with the general public, and remove those names that don’t belong to actual suspects.” (emphasis added)
“Additionally, Mr. Chertoff announced Monday that each airline can now create a system of limited biographical data including a passenger’s date of birth to clear up watch list misidentifications.” (but will they?)