PC could use his social networks to appeal more people, those who are not registered can't see what's happening. PC could post a detail about an event that is going to be held and invite people to it via a link. Maybe that could attract more members.
The Twitter account could get updated more often too. As Jake said, the times when the site is down and when it's fixed could be posted too. And upcoming events, works like "We will be closing the site in X time for X work". PC don't exploit his networks at all and that should change.