It seems the more things change the more they stay the same. Old guard, Mail Art, and new guard, Cell Phone Art, have much in common. They both are very democratic in inviting participation from whoever wants to play.
Early Mail Art was a statement against the juried show system and the exclusivity of the art world, with influences from the Dada and Fluxus movements. Anyone could participate. There was no jury; no fees it just needed to go through the postal system. A network of artists exchanging art through the mail, the more one sent out the more received. When a call for Mail Art went out all artwork received was shown, there was no fee to enter and documentation of the show was sent to all.
Cell Phone Art is sent via email to a network of friends, family and social network contacts. There are no juries or fees and documentation posted to websites.
A great film is How To Draw A Bunny about Ray Johnson (1927-1995) who is considered the father of Mail Art.