The finger mustache tattoo, otherwise known as the "fingerstache", is a tattoo of a stylized mustache on the index finger. The finger is then placed between the nose and the lips, making it appear that the wearer has a mustache. Its particular origin is unknown, however, the recent revival dates to the summer of 2003 in Columbus, Ohio, where a local tattoo artist began tattooing mustaches on friends' fingers as a joke.
I learned about the concept here. It is difficult to believe that this inane concept is actually a trend.
The photo is of a person that I've never met. It is Creative Commons licensed and available on Flickr.