Hey
I can't speak for your other groups, but I've found MakerScan to be an awesome group for discussing and actually doing research and hacking on actual prototype scanners. Having a group filled with enthusiastic people who support the people who do things is often the key to having a positive group and I think we're onto that track here.
As the moderator of this group, if you have an issue with a troll just let me know and I'll take care of it.
Bre
MakerBot Industries
http://makerbot.com