The ANBU are supposed to be staffed with such elite ninja like Anko, Kakashi, Shizune, and Kurenai.
Thus, I have to throw voice in with the "so... why are they about as useful as Storm Troopers in Star Wars?"
We've never seen them do much in the series aside from deliver messages and get trashed by the villain's henchmen (who are later disposed of by teams of genin... makes sense).
There again... the ninja population doesn't make much sense at all. If the Chuunin exams are any indication of how many ninja are actually selected to be Chuunin, the idea that there could ever be more than a few dozen of them at any time is difficult to justify. Jonin, logically, should be even more rare.
So, how there's a ninja war involving a 50 thousand ninja across the four great nations when you have around 12 academy graduates each year (per village) and possibly 4 Cuunin selected every four (per regional exam)... I don't quite get it.
It's probable that I missed some elaboration of Kishimoto's part that makes this all seem much more reasonable (such as other processes for selecting Chuunin or highlighting that naruto's graduating group was merely one class out of an academy that ran multiple classes concurrently across the graduation cycle)
But I realized long ago that the Ninjas did not go by the Numbers.
to protect the jutsu/secrets of the village!