It might depend on the ride. DH and I do the Horsey Hundred every year and we just need to give them our name to get our armbands. We don't show proof of who we are, and frankly, I'm not sure how much they care if somebody has already paid for the registration. If the registree gets something that actually has a name or number on it, I'd ask the person who's taking your registration to change it if they can in case they get in an accident.

We did a ride at a federal armory last year and, for that, we actually had to show ID, but that was for security purposes. I can't imagine that's the norm.