Yeah I remember seeing a similar thread not too long ago. That being said, Team 11's structure for the past two years is:
-Technical Captain (2)
-Mechanical Captain (2)
-Design Captain (2)
-Electrical Captain (1)
-Programming Captain (1)
-Robot
-Website
-Android
-CNC/3D Printing* (1)
-Non Technical Captain (1)
-Scouting (2)
-Business (1)
-Chairmans (1)
-Video/Graphics (1)
-Archiver* (1)
*New this season
The responsibilities of each captain/sub-team are pretty self explanatory. The Technical Captains make the final decisions on robot related matters. Leaders are chosen through an application process that includes creating a resume, interviewing with lead mentors and alumni, and writing several mini-essays. This process also takes into account the student's prior contributions to the team. Leadership is exclusive to juniors and seniors (students can only enter into 11 as sophomores and can't be a leader their first year). This helps us keep the team of roughly 100 members organized.
Freshmen are automatically placed into FRC 193 MORT Beta, which has a much less rigid structure. There are no captains; everyone is exposed to all facets of the robot process. They operate almost completely independently from 11, and are run primarily by alumni. MORT Beta has 50+ members in 2014
We've been doing massive restructuring on 11 for the past few years, especially in 2013 with the inception of 193. We are pretty confident based on the results of this year's build that our current system is effective for our team. That being said, your team structure should be whatever works best for you.