I would say it is important because it holds all the information that would be on a tag, but you can't remove it. I was unsure with Titan at first, "do I really need it.. blah blah blah" But with it only being around $40 for the one I have, and it's a lifetime deal.. it seemed like the best idea, especially because Titan doesn't always have a collar on.
I'm not sure what others are talking about with a procedure, but Titan's was just like a shot, he sat there and they injected it into his shoulder, massaged it for a minute and all was well.
The hardest thing to remember is updating information.. I have read many many success stories with dogs being lost and/or stolen and taken to a local vet or shelter and finding out exactly who to contact. It is really a great idea. And nowadays with the way the world is going, I wouldn't put it past people to want to steal my dog or not return him if he happened to get loose.
Commander Charly Titan (GSD)-15 Jan 2010