I don't know if MS overshipped XBOX360 in 2011 Q4. I will wait till April when MS release 2012 Q1 shipment figure to judge it.
However, we are talking about who will 2011. MS shipped more than 15M+ XBOX360 in the past year. If PS3 shipment figure cannot be over this, it will mean MS won 2011.
Regarding to the negative effect of the "overshipment", I think it would be involved in the topic "who wins 2012".
Just my opinion. I love my PS3 and its games. But I love my XBOX360 more. If someone says "negative" points about 360, I will be a bit of mad. If I offend someone, please forgive me.
I am new here.