It's an old thread but my view on the subject hasn't changed. I don't tag anything unless it's a bag that goes in the hold and those bags have a collection of bronze, silver and gold tags on them. I don't really care what others think, and use them as a way to help identify my bags.

My 3-year-old daughter on the other hand was chuffed to bits when she got a letter with a bronze card and tags; one of those tags is now on her rucksack which she takes on-board. The fact that she achieved bronze on a single flight is utterly meaningless to her, as it should be. Alas, her first collection year expired soon after and she didn't quite reach silver. I did suggest a back-to-back to Tallinn to her but she felt a trip to the play park was a better option.