Lately I've noticed a lot of authors posting their flats. (A flat is the full cover a print book, which includes the spine and back.) In the ebook business, ebooks don't get flats because there's no need for a spine or back cover.
Personally, although I like to see what the whole book will look like, most of the time I prefer to show just my cover. It takes up less room, for one thing. And the front appears much more dramatic without the rest of it.
But curiosity prompts me to ask people if a flat makes any difference when they peruse a cover. Comments?