From what my sister tells me (Her chest being size 'G' =X)
There's a point where they are so big and what not where they basicall say DDD = G.
And random things like that. Her boobs where my size when she was my age (A 'C' cup boarding 'D' cup) but then she had two babies and they went way to big.
So note to self: No babies. Ever.
BREAST REDUCTION! Yeah, it's basically just the opposite of how people get impants because of the way it comes out, but more difficult because they have to remove skin because you wouldn't want a B cup inside and still have the D cup boobs. =O