Right, but forcing people to join could get them to become active. Remember why I came back? Yeah, it was for no reason. You mentioned something about SZ and I decided to take a look for old time's sake. Granted, there was a lot of nostalgia, but look how active I am now? It just took a little push. Could be the same for a lot of potential members.

Also, a lot of members look at member count as a general indication of activity. Because one would think that more members means more active members. Not always true (obviously), but people have that perception. So when they look at SZ with free resources for guests and 2,000 members, why join when they get everything anyway? SI doesn't have resources for guests, but they have 11,000 members, so they must be worth joining, anyway. Probably pretty active.

I don't know how active they are compared to us in terms of active members and posts, but forcing members to join and post at least once to access the resources is enough to possibly garner more activity. Or it could totally flop and then what? Activity stays the same and SZ gets some more members. Not exactly a bad thing.