@tommy2118 Provided a great guide to joining the Destiny Clan. This will allow everyone to have the banner and get achievements like this one. This last option of setting clan was locked before release and requires further attention if not taken already.
I believe the clan size per platform is only 75 for a total of 150.
75 for Xbox, 75 for Playstation includes current and last gen. Not sure if we’ve maxed out for Playstation already. You can have as many followers of a clan as you like though.