There was a rumour (and I stress that's all I heard!) that BMW dealers are doing this as a way of "topping up" your service costs. An example - my old 3 series apparently needed brakes, I didn't let them do it. They had the car 2 months later for some other work and it was never mentioned, I asked (not mentioning the previous service!) and they said "no, your brakes are fine". So I'd be getting a second opinion!

I'm fully expecting my Audi to come back saying it needs new pads next week, but i actually do think they need doing - cross drilled and massive discs - eek!