One of the biggest problems we have right now is that many users don't login before registering for the event. We can't force all event attendees to register though because only some of the attendees are part of our association, some belong to others and attend. We don't allow them to register as there's a lot of hidden info in the system.
What I'd like to see is similar to how paypal works. If the user enters in an email address during registration that already exists they are forced (or at least suggested) to log in first. This would eliminate us going in and manually connecting all these registrations to users that already exist.
I requested this a while back. Basically the system should connect a registration with a user if the email exists in the system. This way you can ensure users get "Credit" for being a member as well as allow non-members to register. It's the only way it's going to work and this is a huge issue for us as well.
Yeah it's a huge pain right now. We've had to go through a thousand entries over the last month and double check that people had logged in. About 90% hadn't. It should also check the the account is enabled as we do have some users with disabled accounts, those can register without logging in (they're not paying association members any more).