Take a close look at what they allot money for: things like travel, books, etc. They'll even tell you that a lot of these are sort of built in "buffers" or whatever, to make sure that if you have some circumstance where you need to commute from DC each day on the MARC or something a bit extreme like that, you'd still be covered more or less. But ask yourself how much you think you'll actually spend on "books" (here's a hint: it'll be a lot less than they recommend), and things of that nature.
Our 4th year expenses included tons of crap that I wont even need to worry about. For instance, I registered for all of Step 2 with the money I had from this year (since I had extra), so by time I got that COA estimate, I already could scratch that off the list. Also, they have a "book" allowance for 4th years as well. Honestly, if anyone bought books for any 4th year rotations, id be throughly shocked, as you can probably use the stuff you accumulated over the past 3 years. Not to mention buying books for 4th year is like buying a car in Manhattan after getting along without one for a few years. Really, it would be just to have one.
Essentially, they assume you are loose with your expenditures and there's no hope for you to be thrifty. Fortunately, most of us are pretty cheap, so there is generally no need to take out the whole thing. If you need all the dough, you have a kid or two, or mortgage you need to make sure gets paid.
I think (but I'm not sure) you can always borrow a little more (up to the COA) if you realize as you go that you didn't take out enough, but don't quote me on that. It's a tough balancing act though, like soccerpunk60 said, because you don't want to get stuck with a ton of extra loan money with building interest. Pretty sure he's right about being able to return X amount of dollars if you borrow too much, but I don't think that window of time is very long.
You can do both, either take out more (if you didnt take out all the money you got offered), or you can give some back before a certain deadline--im not sure what that is though, because i never needed to give back or take more of any kind of money. Although it will accrue interest if you take out too much, its better to take out a thousand or two extra rather than too little, IMHO. You probably want some "Just in case ****" funds, as Chris Rock puts it.
I'm not implying these guys wouldnt echo my sentiments (please correct me if im speaking falsely for any of you), but I just wanted to make sure you knew that, since the worst thing you can do in med school is worry about money. There's far too much else to worry about, especially as you get further and further along.
Shock Trauma. I'm exhausted, but I
). I'm sure shes enjoying Mercy and is gonna become a cutter now. I'm all for that. I'll create my own SBO and/or sigmoid volvulus so she can fix me. The only things I ask of anyone is a) refer me all your MSK/Rehab patients and b) dont 
