If you show interest by applying to join the at-large membership and you have access to the Internet because the process is only accessible via the Internet, then you can belong and vote. There is no satisfactory global organisation of users of the Internet. Potential candidates for bringing together Internet users on a large scale like the Internet Society fall short of the mark. This may well be quite natural. As someone said during the Zurich meeting, maybe the term Internet user ceases to be meaningful when it includes everybody.
Representatives are then accountable only to themselves.
In fact, the at-large representation accentuates one of the major failings of the current representative system in that the link between voters and the elected few becomes too weak. This passion motivates people to travel around the world to defend their cause. It is surely not just the hope of gain. It can no longer be indignation about the NSI monopoly. Something stronger and deeper is at play.