Screenshots should automatically upload and save somewhere off of the headset, (perhaps a new folder/album on Facebook Photos or insta... I'm sure they'll charge for extra storage one day) so that you can easily share wherever you might use a photo on Facebook: posts, comments, groups, your story etc.
You should be able to see, manage, and share these photos in the Oculus app for Android/iPhone that is required for device setup.
It will be great for users and also boost social sharing (i.e. free marketing for Oculus).