Google announced plans to buy Admeld in June to boost its display advertising business. Regulators announced last month that they're taking a close look at the deal, but that doesn't mean it will be blocked -- regulators also took a second look at ITA and DoubleClick, and both of those deals eventually closed.
#5: Postini email security and services, $625 million
Google bought this company in June 2007 and integrated its add-on email services, like spam-blocking and archiving, into Gmail for business users. It's been a critical part of Google's enterprise apps business ever since.
