I had everyone wear name tags at my large (yet very casual) wedding reception after a tiny family-only ceremony.
We encouraged people to write down their names, along with how they knew myself or my husband. That way people had a jumping off point when talking to each other. It was also nice for my out-of-country family to be noted as mother-of-the-bride etc. because hardly any of the reception guests had been to the ceremony.
At the end of the evening, one of my good friends had picked up every departing person's tags and was wearing them all. Very entertaining.
I don't think name tags should be an excuse not to introduce yourself or introduce others, however it is nice reference after introductions have been made. It's also comforting insurance for a bride terrified of forgetting co-worker's spouse's names.