In April of 2005 I might an unusual flight change, by cancelling the return portion of my trip after arriving at my destination. For exactly one year after that point I was "randomly" chosen on every flight I took in the United States, including on the outbound end of international flights. I believe I took around 8 flights within that time period, and was security screened on each one. I became very familiar with the highlighted letters "SSSS", which would appear on my ticket to indicate that I was being screened. After a year though it stopped, and I haven't been randomly selected since.