In by far its largest acquisition to date, Facebook said it will buy photo-sharing service instagram for $1 billion, or about $100 million per Instagram employee. At last, the world will be blessed with a fresh gigantic explosion in Instagram-manipulated pics.

In his official announcement, Facebook CEO Mark Zuckerberg said he was "committed to building and growing Instagram independently," but that doesn't bar him from making the photo tool's (in)famous filters available for use on everyone's Facebook pics. Which means more Sepia and old-timey and low-fi grainy filters on everyone's snapshots, yayyy.

What Zuckerberg was really saying is that Instagram's iPhone app will continue to pipe pictures to rival services like Twitter and Flickr, at least for the time being. That despite the staggering, by Facebook standards, price paid for the 10-person company.

"It's the first time we've ever acquired a product and company with so many users," Zuckerberg said. "We don't plan on doing many more of these, if any at all." Indeed, a quick perusal of Facebook's other deals shows that this is one is 25 times larger than the next biggest, the August 2009 acquisition of FriendFeed.

Back in December, we speculated that Facebook was amassing a $3.5 billion cash hoard (as we exclusively reported) in order to allow for the possibility of a very large acquisition. Given today's cash-and-stock deal, it looks like Facebook got just such an itch.