It's "almost certainly" a hoax, as AllThingsD explains here, but at least it's an entertaining one. The Chive has a series of photos (click here to see them) from a woman who supposedly quits her job as an office assistant via an email to co-workers in which she lays out her reasons on eraser board, one photo at a time. Her boss turns out to be the sexist villain of the tale, complete with bad breath and a serious addiction to Farmville. It's not quite as dramatic as sliding down a plane's emergency exit, but it's still going viral.
As for the hoax part, the brothers behind theChive.com are John and Leo Resig, who run several humor sites. A few years back, one of their sites published a fake story about Donald Trump leaving a $10,000 tip on a small restaurant bill, and it got picked up everywhere. The brothers didn't fess up to concocting this one in an interview with AllThingsD's Peter Kafka, though they admit to a "track record" of similar hoaxes.
(More quitting stories.)