I love doing it in a book shop, it repeatedly confirms that very few people pay attention to what ofter people do, they are generally too self conscious andworried bout what others might think of them.
PhotoReading upside down is handy for books that are sticky and you wind up flipping pages that are stuck together. If you follow on with the intention to PhotoRead the book upside down as well you'll have a great opportunity to catch those pages that you missed the first time through. That means there is no reason to let sticky pages breack the state.
Alex