NEW YORK – Facebook is spending $1 billion to buy the photo-sharing company Instagram in the social network's largest acquisition ever.

Instagram lets people apply filters to photos they snap with their mobile devices and share them with friends and strangers. Some of the filters make the photos look as if they've been taken in the 1970s or on Polaroid cameras.

"This is an important milestone for Facebook because it's the first time we've ever acquired a product and company with so many users," CEO Mark Zuckerberg wrote on his Facebook page. "We don't plan on doing many more of these, if any at all."