Going back on your word happens all the way up and down the poetry ladder.

http://wewhoareabouttodie.com/2010/07/19/behind-the-scenes-at-the-great-paris-review-poetry-purge-of-2010-part-1/

The above is a fascinating story about THE PARIS REVIEW declining to publish previously-accepted poets.

It also reminds me of an incident years ago where the then-host of Midnight Special Bookstore in Santa Monica (a long-defunct independent store) decided to, by fiat, unschedule several featured poets (myself included, for full disclosure's sake) in order to convert the reading to an all open-mike format.

Moral: Disappointment over rescinding of promises happens in all corners of poetry, whether it be a bookstore reading or a prestige literary publication.