The photo album of German World War II propaganda photographer Franz Kreiger. (Tony Cenicola/The New York Times)

The New York Times Lens blog says it identified Franz Krieger (1914-1993) of Salzburg, Austria, after getting important crowdsourcing contributions from two readers: Harriet Scharnberg, a woman studying German propaganda photographs, and Peter Kramml, a man who has published a book about Krieger’s work as a Nazi photographer.

Solving photo mysteries like this one isn’t as difficult as it used to be, with the help of crowdsourcing, viral photos, photoshopping, and social media. But the ease of tracking down photos online can also endanger our privacy.

In 2007, for example, a space blogger did some extensive detective work to prove that the controversial first photo from China’s moon orbiter was photoshopped. Later, Chinese officials proved the retouching was been done by accident, but not before serious damage had been done to the reputation of their space program.

After April’s tornadoes in Alabama, a Facebook page was created to connect lost photographs found after the storms with their rightful owners. Almost 3,000 documents and photographs were posted to that page. And two weeks ago, Melissa Bell and I were able to track down the true identity of “A Gay Girl in Damascus” by matching a photo on a Picasa account with a photo on a blog.

But it’s possible that some of the victims of the tornado and the man behind “A Gay Girl in Damascus” were not pleased that their personal photos were so easily findable online.

New technologies like Facebook’s announcement of facial recognition for photo albums have further increased worries about privacy. European regulators have already said they are looking into banning the technology, and former Google CEO Eric Schmidt called the move “creepy.

Photo search applications like TinEye reverse image search and Google’s new image search, which can help track down an image you already have in your possession, enable everyone from police to stalkers to track where people have once been.

But solved photo mysteries are also giving people hope.

Last week, romantics rejoiced after finding out that a couple caught on camera lying on the ground kissing in the middle of the Vancouver riots was real. The family of the son may have never seen the photo if not for the rapid reproduction of the photo on the Web.

William Kuzmiak looks at a photo from his time as a pilot in WWII. (U.S. Navy Senior Chief Mass Communication Specialist Gary Ward)

When asked for his e-mail address, Kuzmiak told me “I’m not very good at using the computer.” Yet he knew very well that his request wasn’t out of the realm of possibility.