Depending on who you ask, Facebook's new automatic photo syncing feature, which uploads every photo you take on your mobile phone to Facebook, is either a killer feature or something to avoid at all costs. I'm in the latter camp--for at least three reasons.
On one hand, automatic photo syncing is a great convenience. Your mobile pics are backed up instantly, so you don't have to worry about losing all of them in case your phone breaks or gets lost. There are already useful services that do this, however: cloud storage providers Dropbox and SugarSync, for example, and Apple's Photo Stream. For backing up photos, these services, which are meant for storing files and allowing you to easily retrieve all of them, are better suited to the task.
Google+ for Android also has this instant upload feature, for both photos and videos, and it allows for free unlimited free photo storage, as opposed to Facebook's 2GB limit.
I feel there are more downsides to Facebook's auto photo syncing, namely privacy concerns, data usage, and energy usage.
If you enable the photo syncing feature (it's disabled by default, but Facebook prompts you to turn it on), Facebook stores your mobile photos in a private album, "synced from phone." The social network goes through great pains to assure users that only they alone can view their photos, unless specifically shared on Facebook.
If that sounds too paranoid to you and you do trust Facebook with all your mobile photos, consider this: Facebook is now automatically tagging photos with the names of your Facebook friends. If someone takes a photo of you (with or without your permission) and this feature is turned on, you're tagged and might not have anything to say about it.
The second issue is that Facebook uploads every single photo you take. (Once you enable the setting, it'll upload the last 20 pics and then every one going forward.) Not just the ones you want to keep, but also the bad, blurry shots or ones you might not even care about. If you have limited mobile bandwidth, that could eat up a lot of your data plan, even though the app syncs photos at a smaller, approximately 100KB size when on 3G or 4G. Although you can instruct the Facebook app to only upload when you're on Wi-Fi, that's not the default, which means a lot of people might surprisingly go over their data allotment after turning on the feature.
Finally, even when syncing over Wi-Fi, the constant uploading will be a drain on your mobile phone. Although Facebook says it won't sync your photos if your battery level is low, until it determines that point, it'll go on working in the background uploading your photos and using up battery power. (Google+ on Android has a setting where you can sync only when charging, at least.)
I do think automatic photo syncing is an excellent feature and everyone should have a mobile photo backup plan. I just don't think Facebook is the ideal provider of that service. Your thoughts?