Facebook has had this "auto-upload" feature enabled on Android for a couple of months now, but recently the company announced that they have figured out how to enable background auto-uploads on iOS. Although this feature is only enabled for a select few [hundred] people who've been included in the test, it is quite possible that Facebook could roll this out to all users if it proves a success.
This means Facebook automatically [behind the scenes] uploads all the photos that you take with your phone and store them in an unpublished album that only you can see. From then on you can authorize selected photos to be published and made visible to your entire network. By default Facebook will try to upload photos immediately, but you're able to configure this setting to avoid maxing out your data plan. (You can find more in-depth information about this on the Facebook Help Centre, which now notes the feature's presence on iOS.)
Although this sounds like a small incremental change, this new feature is a pretty big deal for Facebook; the company has been capitalising on photos over the past few years more than ever and this feature stands to dramatically boost the number of photos that people post. Google showcased a very similar feature back in June 2011 with Google+ Instant Uploads, however, this release from Facebook could move that beyond just a mere threat.
Currently, between the 300 million images that are uploaded daily to Facebook and its recent acquisition of Instagram, Facebook is winning the photo-race by a country mile. If, and when, it rolls out Photo Sync to all iOS and Android users, and assuming there is no backlash against this, it'll take something special to dethrone Facebook as king of the [online] photograph.