At a Glance: Google’s notable acquisitions

Google Inc.’s planned acquisition of Motorola Mobility Holdings Inc. for $12.5 billion would be its largest ever, nearly four times larger than the previous high, the 2008 purchase of online advertising company DoubleClick for $3.2 billion.

Over the years Google has bought a slew of companies that expanded or complemented the breadth of services that the search leader offers.

Here are some notable ones:

? DoubleClick Inc. (2008). Google bought the provider of online advertising services for $3.2 billion to help it provide more dynamic, multimedia ads besides the short text links that appear next to its search results.

? YouTube Inc. (2006). Google’s $1.76 billion acquisition of the online video sharing site turned out to be a good bet. The site once known mainly for pirated material and home videos of kittens has become an entertainment destination on the Internet.

? AdMob Inc. (2010). Google paid $681 million in stock to buy this mobile advertising service provider in a move to push ahead in this fast-growing market.

? ITA Software Inc. (2010). The $676 million purchase of this airline fare tracker helped Google muscle into the online travel market, though it had to make big concessions in order to clear regulatory hurdles.

? Postini Inc. (2007). Google bought the email security company for $546 million to beef up the security and storage products it offers to businesses.

? Widevine Technologies Inc. (2010). Google paid $158 million in cash for this provider of digital-rights management software, which is used to secure online video content.

? On2 Technologies Inc. (2010). Google paid $123 million for On2, a provider of digital video compression technology, to help cut bandwidth costs at YouTube.

? Keyhole Corp. (2004). This little-known digital mapping service helped propel Google’s maps into the top spot for finding online directions. It did not disclose how much it paid for Keyhole.

? GrandCentral Communications (2007). Google bought this Web-phone service provider for an undisclosed sum and later rebranded it as Google Voice.