For such international event, the media / press photographers such as AP, Reuters, Getty and so forth are the authorised photographers. Of course, our own SPH team and another assigned team will also cover the event.
The above group of photographers will be using DSLRs and wide, mid to super telephoto lenses, etc. They won't use flash as they are all PROs to know the rules unless they wanted to jeopardise their ricebowls. Most of them will be standing at designated areas except a few will be on the fields to shoot.
The spectators on the other hand will mostly using compact to prosumer cameras. Most of them will be using the flash unknowingly. However, given the distance from the seats to the fields, it may not cause too much distraction to the participants. If flash is too obvious, the ushers will intervene and ask the spectator to keep his/her camera.
The next group of spectators will be those who bring DSLRs and mid-to super telephooto lenses to shoot the competitions. However, do you know that it may cause obstruction to others in the view? Image you mounted a monopod with 1D mk 3 and EF 300mm f2.8L at your seat, will you cause obstruction to those sitting besides you and infront? If a lot of people are bring big DSLRs and big lenses, what will happen? I guess that that could be the primary reason from restricting big DSLRs and long lenses at the spectator seats. :dunno: