Everyone wondered if they’d ever really pull the trigger on this, or stick to their adsense guns while DoubleClick ambled along — and the day has come. $3.1B later, Google is now the king of all Internet advertising (although Yahoo! remains no slouch, most recently expanding it’s one-stop online news ad shop to include McClatchy).

Sergey Brin once hinted at DoubleClick being the “life preserver” as John Battelle mentions in The Search (and as Biz2.0 reminds today), but the metaphor was baswed on Adwords going under. While Adsense is doing fine, Google apparently seized on this opportunity to box out Microsoft and go large.

Rafat at PaidContent reports that the $3.1 billion cash offer is “much more than the rumored $2 billion that Microsoft was intending to pay.” It’s also 10 times DCLK (private since 2005)’s revenue.

How will this work out? Here’s Google’s Presser. Battelle’s analysis forthcoming at his blog.