Apparently "Friend Zone" is going into the Oxford English Dictionary, and Amanda Marcotte has some great commentary on it, in her article on Slate, Friend Zone Goes in the OED, and Women Give Up Trying to Let You Down Easy:
In the past, the English language had its fair share of terms to describe the state of being infatuated with a person who does not return your feelings. There was unrequited love for those who prefer more flowery language or crush for those with a more casual flair. Alas, these terms failed on one front: They assigned responsibility for the situation to the person having the feelings. They even went so far as to imply that the object of the affection has no obligation whatsoever to return the feelings (or have sex with someone as a consolation prize). Thus, the angry dudes of the Internet came up with the termfriend zone, which shifts the locus of responsibility from the subject to the object of the crush. It implies that, as the object is at fault for "putting" her admirer into the friend zone, it is her duty to do something to remove him from it, preferably by getting naked.
Unsurprisingly, the masses are fond of this new term. (And let's be honest: While men and women of all sexual orientations get crushes, the friend zone is mostly a straight-male phenomenon based on the widespread sexist belief that straight men can never truly be friends with women without having an ulterior motive.) It’s so popular, in fact, that it is now being put in the Oxford English Dictionary, a sacred tome widely believed to be both a better dictionary and a better step stool than, say, Merriam-Webster.
After that, she says some mean things about Bronies and Reddit users -- which isn't totally unfair -- and encourages women to keep an eye out for Friend Zone style self-pity and shut it down hard.
Since "Friend Zone" is getting acknowledged by the OED, I'm glad someone's pointing out that there are ways to say "I'm bummed out that someone I like isn't into me," without saying "and they're wrong for feeling that way."