Kindle Fire's Success

The biggest tablet development last year was the emergence of Amazon as a major player. The online retailer shipped 4.7 million units of its , enough to take second place with 16.8 percent of the worldwide market.

"Amazon's widely-reported entry into the media tablet market with a $199, 7-inch product seemed to raise consumers' awareness of the category worldwide despite the fact that the Fire shipped almost exclusively in the U.S. in the fourth quarter," said IDC analyst Tom Mainelli in a statement.

The was the driving force behind Android's market-share rise: up from 32.3 percent in the third quarter of 2011, to 44.6 percent in the fourth. (The Fire runs a custom version of Android.)

Samsung's share grew slightly from 5.5 percent in Q3 to 5.8 percent in Q4. And while Barnes & Noble increased its tablet shipments, its market share actually slipped in Q4 to 3.5 percent, down from 4.5 percent.