This weblog essay by Teresa Nielsen Hayden — a person who actually writes rejection letters — is worth looking at. It’s sociologically interesting, funny and a little sad (note: link by way of The Elegant Variation).
My only quibble: rejections are sometimes (if rarely) personal. It does happen that an author has a history with an editor or a house. I once was confronted with accepting or rejecting something written by a former student of mine, somebody who had not endeared him/herself to me. How can that not be personal on some level? And before you ask: I rejected it. It just wasn’t good enough to make me swallow my dislike. And no, I didn’t use a photocopied rejection letter. And yes, s/he almost certainly felt affronted/insulted/poorly used.
My own personal favorite rejection letter was from the editor of The Atlantic Monthly, two lines long (and refering to my Other Name) “The Lippi-Green in a story-teller. Try us again?”