irontwig
Veteran
Larger, yes. Much larger, I don't know.
WCA has 21743 members who's doing 3x3x3 : http://www.worldcubeassociation.org/results/statistics.php#most_persons
Speedsolving has 17415 members : http://www.speedsolving.com/forum/memberlist.php
However, I see your point.
Well, I'm not sure of the reliability, but apparently the mf8 forum has 166,803 members and 1,643,470 posts.