There really isn't anything there I can disagree with.
We have to be realistic. Before we can start talking about imposing a rule to be enforced (which was the purpose of the initial proposition) we have to consider the implications. If we aren't going to remove posts that don't include that information then the notion of a rule becomes a nonsense and it becomes a request for a courtesy. In which case I maintain the best modus operandi is to lead by example.
People are already adopting this habit anyway, especially with events or fashion photoshoots where the information continues to be available. Why become tub thumpers about it? We want to encourage people to contribute not disuade them from doing so. Show them a better way and they'll see the advantages.
As big a pain in the arse as it is, manual checking will always be a fact of moderation and of regular contribution. To my mind it's neither practical nor sociable to force people into providing a shortcut.
BOC
I should reply to this since I believe I'm the mod who gakon referred to as stating what a pain in the ass it can be to search a large thread for duplicates. First of all, I don't think gakon (or me or anyone else who would favour this proposition) would like to have any posts without such information removed. Obviously, there are times when that just isn't possible. Even those of us who are extremely diligent in trying to provide info sometimes have to post images without it. I've always been of the mind that providing such info - when available, of course - is in the best interest of posters, collectors and mods checking posts.
This is supposed to be a community where we are all working together to provide the best quality images to each other, but the reality is that it's become more of a platform for the post whores to either fill their pockets or their egos.
Addendum
"This is supposed to be a community where we are all working together" This is why we have a report button. Moderators are human and fallible just like everyone else and members are actively encouraged to report duplicates and other rule breaches that we may have missed so we can act on them quickly and decisively with minimal fuss. We have mechanisms in place to catch the bits that are missed. Generally speaking, regular contributing members are superb at letting us know about those things that slip under the wire. Though no system is perfect, generally speaking, and when egos don't get in the way, this works quite well.