With the recent arrests of suspected terrorists in London, safety and security have been on the minds of many people around the world.  The worst moment I can remember taking place on the tennis court occurred in Germany in the early 90s when a deranged fan walked onto the court during a changeover and stabbed Monica Seles in the back.  Fortunately, Seles eventually recovered although her career and life were never the same afterwards.  Since then, there have been many changes in security both on court and for fans entering tournament venues.  Therefore, it was very disturbing to see that two fans, just having fun, were able to easily walk onto Centre Court at Wimbledon in early July.  One was a streaker and the other fan just swung a racket a few times before being escorted off the court.  Security at the 2006 U.S. Open tennis tournament seemed to be even tighter than it has been in the past.  And Tennis Australia developed a beefed-up security plan with the ITF to make Lleyton Hewitt feel comfortable traveling down to South America for the Davis Cup Semifinal matches against Argentina in mid September.  Hewitt had expressed concern for his personal safety because he had had tense matches with both David Nalbandian and Guillermo Coria in the past.  The charged atmosphere of a Davis Cup match in Argentina worried Hewitt.  Hopefully, this will not signal the beginning of top players traveling with security details in addition to their regular entourage of coaches, stringers and massage therapists.