Internet search engine giant Google Inc.'s $12.5 billion acquisition of Motorola Mobility has shocked market watchers because the handset maker is struggling to keep pace with bigger Android rivals like Samsung and HTC -- but the deal could actually turn out to be Google's best move ever.

Google on Monday dipped into its $39 billion cash reserve to buy Motorola Mobility -- lock, stock and barrel -- for $12.5 billion, or at 63 percent premium over the target stock's Friday closing price.

The acquisition, Google's largest ever (the previous largest acquisition was purchase of DoubleClick for $3.1 billion in 2007), shocked the Wall Street, making Google's stock dip 2.6 percent to $549.23 soon after the announcement.

Investors were stunned because Motorola is not only the smallest of the major Android smartphone makers but it is also the only major Android handset maker whose share of the smartphone market declined in the second quarter. Motorola split into Motorola Mobility and Motorola Solutions Inc. in the first quarter of 2011.

While Motorola Mobility is responsible for making smartphones and consumer products such as burglar alarms and wireless routers, Motorola Solutions is into networks business and enterprise mobility solutions.

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However, Google's move could be its best ever -- and there are 10 reasons why.

Start the slideshow to see why Google is willing to pay so much for Motorola Mobility.