Have you ever been tagged in a photo only to untag yourself immediately for one reason or another? It’s a common problem and it’s something that Facebook could easily resolve by requiring user to approve all photos they’re tagged in or have some sort of delay before tagged photos appear to all users. The rationale is that there’s no clear benefit of allowing users to instantly tag a user.
Facebook benefits from the photo tagging process in that it increases user engagement. By introducing a photo tagging approval process, Facebook would still experience increased engagement as users log in to check the photo they were just tagged in. While Facebook would need to ensure that the majority of users are not untagging themselves from all photos, it would present a layer of security that only privacy settings currently enable.
Alternatively, Facebook could also make photo tagging a more granular feature. The argument against that would be added complexity to the existing photos application will make it harder to use. Also, why change what is essentially the most popular photo application in the world? Both arguments are legitimate, however I can’t say how frequently I get tagged in photos which are not relevant to me.
While I doubt this is as much of an issue for the average user, I can’t tell you how many people I’ve seen tagged in photos which are the equivalent of spam. While I’m not exactly laying out well structured argument for a Facebook photo tagging approval process, it appears to make a lot of sense and there are very few downsides to it.