There's been a lot written about this problem with Triumph Bonneville spokes breaking - here is my experience.
I bought a new T100 Bonneville from Ongar MC's in Jan 2005. Last Spring I noticed that a spoke had broken on the rear wheel.
Took it to dealer in York - A1 Moto - who said they would contact Triumph for a warranty claim on a new rim. I was given a demo bike for two days then told it was ready to collect
Collected bike then two days later noticed another spoke was adrift. Rang the dealer again who asked me to take a pic of the mileometer (2500 miles) and the spoke and send it by email to them with a snotty note to forward to Triumph - which I did.
Heard nothing for a couple of weeks then chased them and was told that they had approved a new wheel. Booked back in and waited, told by dealer that the hub nuts were all rounded and had I had the wheel off at any point (I hadn't). Anyway they fixed it all and so far so good.
They did tell me that Triumph needed my photos for a meeting with a supplier. I asked them if they had had any more and they said just one Speedmaster.