Solipists unite!
-Arizona Hot
Seems like the society would be highly inefficient. Every person in attendance would have to take attendance even though it would always be 1. Likewise all matters put to a vote would pass 1 to 0. That is unless there are procedural rules requiring a quorum. If the quorum is greater than 1 nothing would ever happen.
The single solipsist in attendance is likely to be a reformed procrastinator.