Terms like "running back by committee" and "two quarterback system" don't necessarily stem from positive observations by a coaching staff. More often than not, what is said (by these terms) and what is meant are two completely different things.
It could mean the team in question has incredible depth and competition (see USC).
However, when I hear most coaches say these things, I cringe at the prospect of what is actually meant. When a coach says we are running a two quarterback system or running back by committee, it means nobody has stepped up or separated themselves enough to really show they are a clear starter.
In other words the team in question has decent scholarship players at the position, but nobody special.
There are exceptions to the rule, but even then, playing two guys at quasi-equal snaps at the same position isn't generally what is best for any offense, especially at the quarterback position.
Two quarterback systems can work, but rarely are the best of the two options.
Ideally you want a quarterback who is the clear starter you can build your offense around, and a backup or two that give you the ability to win games if necessary. This is particularly true at schools like Michigan, where you have a traditionally strong recruiting base and coaching staff that can develop strong players within their system.
Having said that, their are again exceptions to the rule, and the 2009 season is an example of this for the maize and blue. A lot has been made out of our quarterback situation this offseason, with the prospect of starting a true freshman come Sept. 5.
In the midst of the speculation of freshmen struggles, allow me to point out that Michigan isn't stuck with one option for any particular game. They have two young guys that can compete and hurt opposing defenses in different ways.
Also, having two guys lowers the chances that they will both be a bust.
On the the one hand you have Tate Forcier, who has been on campus since January and has a head start in learning the offense and reading coverages. Tate is a dual-threat quarterback who fits the scheme, but is also more of a balanced dual-threat.
He isn't the best pure passer, but he is very very good at throwing in and out of the pocket, and has a quick release and sublime timing that lead to accurate passing.
He isn't the best runner, but has excellent speed for a quarterback, especially one who has accomplished as much as he has as a passer. When you put his skill set together, you have a guy that is a dangerous weapon because he brings balance to the table.
Denard Robinson is maybe one of the most underrated passers in his class, and what he may lack in ideal height he makes up for with raw speed. There may not be a faster quarterback option in the entire Big Ten, if not the nation, with his 4.3 40 yard dash speed.
Like Tate, Denard is also more balanced than he probably gets credit for. Robinson isn't just a runner, and Forcier isn't even that much slower than Robinson in terms of game speed and scrambling.
They are both complete players who have just enough of a difference in their skill set to make teams have to game plan for subtly different offenses.
I'm not a big fan of two-quarterback systems, but when you have two true freshmen, competition is key because it makes the guys sharper, and give the coach options.
As the saying goes, "two heads are often better than one." Michigan is most likely a strong case in point right now.