From a Paul "Infectious Greed" Kedrosky post on Photoshop techniques:
Taking it up a level, what is happening here is that tourists are just another kind of outlier digital data in a digital database, otherwise known as a photo. Like cleaning spurious data from traditional data sets, which has gone on forever, related ad hoc techniques are now appearing in the consumer imaging world. Fascinating.
Tourists are spurious data! I love that conceit. Since I walk home through the throngs of out of towners gwaking at the show windows of Fifth Avenue, I only wish that it were so in real life.