Oh I think this is a great idea!
This isn’t too much different to conf/camp/event swag, but this is even better because you get to actually hang on to it for a long time. Its a nice reminder of all the awesome things you’ve been to, without any of the overhead of physical swag.
I love getting conf t-shirts and all the swag, but I am sometimes guilty of hanging on to them only for the memory and they sit at the back of the cupboard, which I think is wasteful.
Having something like a badge for all the things you came to is a great way of fostering a strong sense of community. I don’t think it is a barrier or unfriendly for new comers or those that can’t attend events, like Toby said. Just a thing that said you were at this event.
Would love to see this implemented!