It's based on post counts, unless you're in a special group. There's a couple of different backer groups, depending on donation amounts, and the bosses etc that you mentioned. Otherwise, you move up a level as you hit the post counts.
Recruit - 0 Posts
Lackey - 50 Posts
Villain - 100 Posts
Senior Villian - 250 Posts
Mastermind - 500 Posts
Just checked it out, there's nobody who isn't on the production team in some form that is above Lackey.