Hi, I was hoping to get a little perspective on this issue.
My sister recently joined a large martial arts club which meets 3 times a week. Because the members spend so much time together (they tend to go to the pub after jitsu) they have all friended each other on Facebook.
One member, a longstanding personality within the club, created a invite-only, very secret, Facebook group for a few close friends that she'd made through the club (maybe 15% of the club?). No other club members know about the group, and they don't mention it to other people. The leader was not Invited to be in the group, because they didn't want her to feel obligated to make the group official- it's just a load of friends with one common hobby, and really very benign.
When the club Sensei found out about the group (through some fairly dedicated snooping), she lost it and started asking various people for information. When that didn't work, she decided to ban anyone who may be in the group from attending the club. It's left a bit of a sour taste in people's mouths to say the least, as it was only very rarely that the club was even mentioned in the group.
How far can this club leader go to restrict club members behaviour online, away from the club? Is it fair?