I would never NOT have my dogs licensed.
Any thing that would help them get found if in the case they're lost is a good thing to me. It's law here that they are licensed, and they aren't allowed to go to many places if they aren't.
To get lincenses here, your dogs must have their shots.. which is great because if gives you a general idea at which dogs have their shots, which don't when you meet them.
I think it's a GOOD law.