Did you know that in 2000, there were about 2.2 million payphones across the United States? Or that there are still about 500,000 operational ones? Or that they handle roughly 1.7 billion calls a year? I didn't know that until about five minutes ago, and neither was I likely to before Dan Marker-Moore dropped me a note about #payphoneography, his ironically inspired project to photograph public telephones with the very device that has contributed to their demise.

#payphoneography started in December 2011, as a personal piece of fun in Dan's corner of California. See a payphone, snap it, share it. Before long, people as far away as Australia had been photographing and sharing images of public telephones using #payphoneography on Instagram, Facebook, and Twitter. Dan says it's been fascinating watching the idea catch on, both spontaneously and as the result of his carefully crafted stickers.

'I made stickers that fit perfectly on the handsets that say #payphoneography. Without any instructions people see the sticker and know how to share. They pull out their mobile phones take a picture and include the hash tag #payphoneography when they share it.'

At the moment over 4,000 images have been contributed to the cause from countries including South Africa, Russia, Italy, and Japan. But Dan says that his favourite phones are from São Paulo: 'Their phones are surrounded by a suspended dome booth and feature bright yellows and blues. Recently these phones were featured in art project where they were transformed into sculptures and paintings.'

And yes, Dan says that a phone has started to ring just after he'd photographed it. He checked very carefully for a lurking Kiefer Sutherland before he answered it, only to be met by the screeching of a fax machine on the other end!

With a 4,000-strong international portfolio, where do you go next? Well, Dan would definitely like to start photographing overseas phones for himself. But he'd like to get the project into print, too.

Want to take part? You know what to do! Want to look at payphones from across the globe? Head the #payphoneography website: blog.payphoneography.com