The sheep industry has had "premise id" for many years. If you raise sheep or goats, you received a premise number and any time you sold an sexually intact sheep for ANY reason, the tag had to be in the ear and recorded by the seller. Example: If you sold fat lambs at a sale barn that were ewes and rams that were not castrated, each of them had to have a tag. If you sold a show ewe to a youth, it had to have a tag.
As far as I know, there has been no issues, except only ONE company was given the gov't contract to make, sell, and distribute the tags. The quality was poor, and while the tags were at no cost to the producer (only the gov't was charged), the taggers were an expense of the producer. A cheaply made, plastic tagger was $25. Again, the producer was not charged for the tags, but the gov't was. Not sure how much the gov't was charged but I am sure it was too much for again, a cheaply made tag that fades within a few years due to poor ink.
If they are going to require a metal tag in cattle's ear, they better train the vets on how to put them in. I finally quit having them put in after many of them stuck up because they were not put in properly and the metal tip not bent down and "hooked". Ripped too many ears.