I would strongly suggest you not do so.
I'm going to go against the crowd and say go for it. Just to see what happens.
The letter you will receive:Dear Applicant:While we appreciate your decision to apply to XXX Law School, we are limited in the number of applicants we can accept for the incoming class of students. While we recognize the achivements you have accomplished thus far, due to limitations in class size, we regret to inform you that we must reject your application at this time. No, seriously, it's not you- it's us.Sincerely,Walter A. Adcomm, IIIThe ensuing phone call to a friend, who happens to be an adcomm at a different school:-You won't believe what I got in the mail today. Somebody we rejected sent us a letter wanting to know why we couldn't take them.-Really? Did you give them that BS about class limitations?-Well, yeah. It's just kind of presumptious that people want an individualized letter telling them exactly why we couldn't take them. I mean, come on, they were below our medians- how did they get this far in the process?-That is kind of sad, come to think about it. Who is this person, anyway? I want to make sure we don't have this guy coming to our law school and demanding an individualized letter from the teacher every time he doesn't get an A+.Think it couldn't happen? Who knows, maybe it couldn't... I wouldn't risk it. Not considering they will never give you the real reason- your numbers weren't up to snuff.