USN (as of 27 May 2011):
# of "deployable battle force ships" = 286
# of acdu Admirals of all ranks* = 304, with another 24 selected for Rear Admiral (when a slot opens up) [this is the number of names on the biography list cited below]
# of acdu USN officers = ~52,581
# of acdu USN personnel = 328,051
Thus, the USN has 1 active duty Admiral (of all ranks) for each 1,079 overall personnel.
Status of the Navy
US Navy Leadership
United States Code: Title 10,526. Authorized strength: general and flag officers on active duty | LII / Legal Information Institute
* this number varies, as it is very dependent on how many Admirals are in "joint-duty" postings.
US code title 10, subtitle A, part II, chapter 32, section 526 limits the USN to 160 active duty flag officers... but then exempts all flag officers serving in joint-duty, and sets a minimum number of 61 such active duty flag officers, for a minimum USN Admiral establishment of 221.
Of course, they serve in such vital positions as:
Rear Admiral Philip S. Davidson; Senior Military Advisor to the Special Representative for Afghanistan and Pakistan