Ecommerce:

• Amazon.com quietly acquires the social shopping whizzes at Quorus.

• Online merchants home in on imbibing consumers.

Mobile Marketing:

• The trouble with in-app advertising.

Social Media:

• Google+ service may have 400 million users by end of 2012.

• YouTube Slam pits viral videos against each other.

Mobile Computing:

• Apple vs. Android: Who won the Christmas bake-off?

• Android and iOS see record breaking activations on Christmas day.

• 50,000 apps later, Windows Phone is still in trouble.

Global Business:

• Beijing launches its own GPS rival.