Some contests and festivals can be exploitative. They may require large submission fees and then grab rights from the winning writers or photographers based on language in the submission contract.
In some entry guidelines (for instance, in the Emerging Writer Awards), submitting an entry grants publishing rights.
Writers who don't read the fine print carefully enough may find themselves trapped by such provisions. See: http://accrispin.blogspot.com/2015/06/awards-profiteers-how-writers-can.html
To reduce such exploitation, the Dramatists Guild has issued a statement on "Best Practices for Festivals and Contests". A good idea.
Now it is up to contest organizers and playwrights today attention to these guidelines. Here is the one-page statement with the language of the release preceding it.