Also, thanks everyone for the info on Kim.
It still doesn't make a lot of sense to me though. I figured being a "senior" officer meant that you'd had a lot of experience in the field and you were qualified for a position of some authority. It doesn't make much sense to me for an ensign to be made a senior officer right out of the academy. Especially someone as incompetent as Kim...or maybe I'm just biased against him because the actor can't act...
In most navies, air forces, armies etc... There's at least ten enlisted personal for every officer, and the same is probably true for Starfleet. Just because Kim was the lowest ranked officer, he still outranks 90 percent of Starfleet, who are extraordinarily more qualified and experienced in their particular fields than the people telling them what to do, as in the case of lads like O'Brien who've been at this for 20 years but still have to take orders from children still wet behind the ears.
Below is two years old, referencing the US Navy.
As of today's date there are:
273,865 Enlisted Personnel
Which equates to about a 5:1 ratio of enlisted to officer.