Facebook photo upload support has been added to the Nintendo DSi. The feature was actually added on August 3rd. The feature was added after a system update. Facebook integration was added in the camera/photo gallery module. Your Facebook account can be set up by selecting the icon next to the Star, Shamrock, and Heart.
Tapping the Facebook icon causes a pop-up to appear. There is a Facebook login page that appears in the pop-up. Once you enter the information the first time, it remains auto-filled after that. After selecting a photo, you confirm that you want to upload it. After uploading the photo, it appears in an album called “Photos from Nintendo DSi” on Facebook.