I read somewhere that the lightest carbon frame can be an unstable, uncomfortable ride.

My present frame is about 1000gms, and I like the way it handles. I am thinking of buying a new frame, and ever lighter seems to be the mantra these days. I have heard a bike enthusiast I respect lament why Colnago has really not done much regarding making their frames lighter in recent memory, and he thus feels they are overpriced for what you get, and that is why he won't buy one right now.

Can you framebuilders weigh in on where the sweetspot is on carbon frames weight-wise? I mean, what is too light to handle superbly? And what is too heavy to not get the benefit of lighter weight.

Thanks.