Seems like a funny policy to not backup production paying customers photos & metadata. Think of all the photos, comments, followers, etc that just got nuked! Seems like they rely on RAID or having multiple copies of the data spread around for disaster recovery. Sure it protects you from a server/raid/hardware failure but when a user/admin does something dumb it can really hurt!
Doing a quick google search turns up this gem:
Staff - heather says: "When an account is deleted, photos and any metadata associated with account is queued and deleted. If not instantaneous, it's removed within minutes."