The iPhone 3G battery is shit

My iPhone 3G is behaving like a total dog when it comes to battery power. I got on the train at 10:11am with full battery, right? I switched on the mp3 player, I checked some email, I arsed about on Facebook, I located myself a few times, blah de blah. I generally ‘used’ the device for the duration of the 35 minute train ride. I was down about 10% of the battery power by the end of the journey.