I'm one of 3 and it seemed quite the norm when I was growing up - my perception was lots of families of 3 children. Now I and majority of friends have 2 DCs and I'm surprised that it seems automatically accepted you've had your children when you reach 2 and that you'd be 'brave'/'mad' to go on.
We're contemplating no 3 but occasionally wonder if everyone else knows something we don't :) I know every family situation is different but have I missed something?