To facilitate interaction between guild members I would like to encourage everyone already in this steam group to contact our guildies in-game and let them know to hit me up on steam so I can add them here.
Alternatively, as all members of this steam group have the ability to invite, you guys can even take the initiative and add them yourselves. :3

~Senobfoliah

PS: Don't forget that you can access the group chat by clicking on 'display friends list', selecting the groups tab and double clicking on the avatar (or right click).