Last night Michael Bishop, who is in Seattle to teach the first week of Clarion West, gave a reading at the University Bookstore. He read a selection of three very short SF stories and an SF poem, all of which were well received. One of the stories was, he said, an experiment. He had heard of another author who wrote a story entirely in questions and decided he wanted to try the form for himself. The result was a monologue by a college professor who has been interrupted in his office by a hapless student. The audience laughed throughout, both at the cleverness of the form and the psychological acuteness of the content. Michael knows his teacher-student relationships.
Writers like to do this sort of thing. I once read a frame story in which the author used the frame to directly harangue the reader. Immediately I sat down and used the same form to write "Casey's Empire." I know of another writer who, after coming across Terry Bisson's "They're Made of Meat," wrote a story entirely in dialogue. Sometimes these experiments don't work (notice I'm not giving the Bisson-inspiree's name). But even when they don't, they represent efforts to expand one's range.
More serious borrowings can include trying to imitate another writer's style (my first novel was a direct set at Peter Beagle's lush style, a fact noted by every single reviewer who noticed the book). Plot patterns, too, are fertile ground for imitation. You can make the argument that Ursula LeGuin's "The Dispossessed" uses the same plot as Frank Baum's "The Wizard of Oz," and that both hark back to the fairy tale "City Mouse, Country Mouse."
An important point: Such borrowing are not theft. They are, instead, "acts of homage." :)