Google's $12.5 billion purchase of Motorola will be its biggest acquisition ever -- more than four times the size of DoubleClick, the previous leader.

But over the last decade, Google has been one of the biggest -- and most successful -- acquirers in the tech industry, and owes a lot of its success to these smart buys.

Its core search advertising platform and most of its biggest new businesses, including Android, YouTube, and display advertising, all come from other companies.

Join us as we count down Google's top 16 acquisitions by value and show what happened to them.